J. Bryan Jones's research while affiliated with University of Toronto and other places

Publications (192)

Article
Pig liver esterase-catalyzed hydrolyses of dimethyl 3-hydroxy-, 3-methoxyethoxymethoxy-, and 3-benzyloxyglutarates occur with enantiotopic stereoselectivity to give the corresponding acid-ester products of 16–40% enantiomeric excess (ee). The results also provide another example of reversal of PLE-stereoselectivity.
Article
Preparative-scale pig liver esterase-catalyzed hydrolyses of five-membered ring meso-1,3-diesters are enantiotopically selective. While pro-S enantiotopic selectivity is exhibited in each case, the absolute configuration sense of the hydrolysis in the cyclopentyl series is opposite to that of both the tetrahydrofuranyl and tetrahydrothiophenyl dies...
Article
The synthesis of enantiomerically pure (+)-grandisol has been achieved from an enzymically generated chiral synthon. The synthesis is an efficient one, the yield of optically pure material being 12% up to the penultimate step and 3% overall.
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Full-text available
The effects of buffer, pH, reaction time, and [enzyme]/[substrate] ratio on the enantiomeric purities of the alcohol products of horse liver alcohol dehydrogenase-catalyzed reductions of (±)-α-alkylcyclohexanones and -tetrahydrothiopyranones have been studied. For poor substrates of this type, formation of enantiomerically pure products is assured...
Article
The preparations of ten decalindiones for investigation as substrates of horse liver alcohol dehydrogenase are reported. The structure characterizations include clarifications of some ambiguities in the decalin literature.
Article
Preparative-scale horse liver alcohol dehydrogenase-catalyzed oxidation of mesoexo- and endo-7-oxabicyclo[2.2.1]heptane diols provides a direct one-step route to enantiomerically pure chiral γ-lactones of the oxabicyclic series.
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The formation of cis-2-alkylcyclohexanol products from horse liver alcohol dehydrogenase-catalyzed reductions of 2-alkylcyclohexanones has been detected for the first time. The cis-alcohols are minor (<4%) products, with the isomeric trans-products being heavily predominant under all conditions. cis-Alcohol production can be suppressed by suitable...
Article
The effects have been evaluated of up to 50% (v/v) of methanol, tert-butyl alcohol, dimethylsulfoxide, sulfolane, acetonitrile, dimethylformamide, N-methyl-2-pyrrolidone, hexamethylphosphoramide, acetone, 2-butanone, tetrahydrofuran, dimethoxyethane, diglyme, and dioxane on horse liver alcohol dehydrogenase (HLADH)-catalyzed oxidation of the repres...
Article
Full-text available
A synthesis of the civet constituent, (+)-(S,S)-(cis-6-methyltetrahydropyran-2-yl)acetic acid, is described, in which the key stereochemistry of the chiral starting material is set by an enantiotopically selective, porcine pancreatic lipase-catalyzed, hydrolysis of a meso diester.
Article
Pig liver esterase (PLE) catalyzed hydrolysis of racemic piperidine esters proceeds enantioselectively to give product acids and recovered esters in 0–47% enantiomeric excess.
Article
The potential utility of the L-lactate dehydrogenase of Bacillusstearothermophilus (BSLDH) for stereospecific, preparative-scale reductions of α-keto acids to (S)-α-hydroxy acids of > 99% ee has been demonstrated. BSLDH is a stable, thermophilic, enzyme whose gene has been cloned into a high-expression vector to assure its plentiful supply. Its spe...
Article
Factors involved in controlling and predicting the structural specificity and stereospecificity of synthetically useful enzymes, including pig liver esterase, subtilisin BPN′ and Carlsberg, α-chymotrypsin, and an L-lactate dehydrogenase, are discussed.
Article
The reactions of 2-lithio-1,3-dithiane with both 2α,3α- and 2β,3β-oxiranyl-5α-cholestane have been used to prepare both epimers of 2-methyl-3-oxo- and 3-methyl-2-oxo-5α-cholestane. The results obtained illustrate the potential of the dithiane-epoxide route as an attractive and versatile general procedure for the stereospecific introduction of subst...
Article
The potential of 2-lithio-1,3-dithiane reactions for the introduction of corticoid and related C-17 functions into the steroid nucleus has been explored. Although attempts to effect the direct addition of the dithiane reagents to C-17 ketones met with limited success, reactions of C-17 spiroepoxides were found to provide a convenient entry into rou...
Article
Full-text available
The rates of H-transfer between various 1,4-dihydropyridines and pyridinium salts (including NADH and NAD+), and from 1,4-dihydropyridines to FMN, have been measured. The reactions are found to be sufficiently slow for H-transfer to be rate-determining to a significant extent when such Systems are applied for nicotinamide coenzyme recycling purpose...
Article
Full-text available
2-Hydroxymethyl- and 2-acetoxymethylbenzimidazole, and their C-4(7)-carboxy derivatives, have been synthesized and characterized for evaluation as chemical models of the Asp-His-Ser triad present at the active sites of several serine proteases. Preliminary studies of the 2-acetoxy compounds, which are analogues of the acyl enzymes, show that the ra...
Article
The α-chymotrypsin-catalyzed hydrolyses of a representative spectrum of (R)- and (S)-2-butyl, -2-octyl, and -α-phenethyl esters of N-acetyl-L-phenylalanine, N-acetylglycine, α-hydroxy-β-phenyl-propionic, dihydrocinnamic, and hippuric acids have been examined. The kinetic studies were carried out in order to provide data on the practicability of exp...
Article
A new active site model for predicting and interpreting the structural- and stereospecificity of horse liver alcohol dehydrogenase-catalyzed oxidations and reductions has been formulated from the specificity, X-ray, and kinetic data now available. The new model is based on a cubic-space system and is convenient and easy to use. The model is complet...
Article
Full-text available
The effects have been evaluated of up to 30% (v/v) of methanol, ethanol, 2-propanol, tert-butylalcohol, dimethylsulfoxide, sulfolane, acetonitrile, dimethylformamide, N-methyl-2-pyrrolidone, hexamethylphosphoramide, tetrahydrofuran, dimethoxymethane, diglyme, and dioxane on horse liver alcohol dehydrogenase-catalyzed reduction of the representative...
Article
The asymmetric synthetic potential of horse liver alcohol dehydrogenase catalyzed oxidations of variously 3-substituted pentane-1,5-diols has been further delineated. The oxidations proceed with enantiotopic selectivity to give the corresponding (3S)-3-substituted valerolactones of up to 78% ee. The reactions occur via initial oxidation of the pro-...
Article
Full-text available
The high cost of nicotinamide coenzymes currently acts as a deterrent to the widespread adoption of alcohol dehydrogenases as chiral catalysts for effecting stereospecific and selective oxidoreductions on a preparative scale. Attempts to overcome this problem generally involve using catalytic amounts of coenzyme together with an auxiliary system ca...
Article
The esterolytic activities of native chymotrypsin (CT) and immobilized CT-Sephadex have been studied in the presence of up to 20% of the organic solvents methanol, ethanol, 2-propanol, tert-butyl alcohol, dioxane, or DMSO. The general cosolvent-induced inhibition of the native enzyme was attenuated for immobilized CT. Most noticeably, the apparent...
Article
The influence of a range of protic and aprotic solvents of varying polarities on the enantiomeric specificity of α-chymotrypsin has been examined using methyl (2S)- and (2R)-2-acetamido-2-phenylacetate (1) as representative L- and D-substrates. The rates of hydrolysis were determined in solutions containing up to 30% organic solvent. The addition o...
Article
The specificity of horse liver alcohol dehydrogenase (HLADH) with respect to unsubstituted five-, six-, and seven-membered ring 3- and 4-thiaketone and -thiaalcohol substrates has been examined. The enzyme is found to have a broad tolerance of the structural variations within this series. HLADH also exhibits encouraging (up to 46%) enantiotopic and...
Article
The substrate specificity of acetimidylated (A-HLADH) and hydroxybutyrimidylated horse liver alcohol dehydrogenase (HB-HLADH) has been evaluated for the ethanol–acetaldehyde, trans-2-hexenol–trans-2-hexenal, furfural–furfuryl alcohol, benzaldehyde–benzyl alcohol, cyclobutanol–cyclobutanone, cyclopentanol–cyclopentanone, cyclohexanol–cyclohexanone,...
Article
The scope of the reactions of lithio-dithianes with spiro-epoxides for various stereospecific functionalizations of alicyclic systems has been illustrated by their application to spiro-3α- and -3β-oxiranes of the 5α-cholestane and 5α-androstane series.
Article
Full-text available
Horse liver alcohol dehydrogenase has been shown to be effective in catalyzing regiospecific oxidations of only the primary alcohol functions of several cyclohexane substrates possessing both primary and secondary alcohol substituents. The reactions, which were all performed on a preparative scale, were also enantioselective in some cases.
Article
Studies have been carried out which delineate some of the factors involved in the exploitation of α-chymotrypsin as a catalyst for the specific hydrolysis of selected aromatic ester protecting groups under mild conditions with a specificity not achievable by non-enzymic reagents. The reactions can be carried out under heterogeneous conditions and e...
Article
The direction of the diazomethane ring enlargement of 17β-hydroxy-5α-androstan-3-one (I, R = OH) appears to be controlled by the long-range effect of the 17β-hydroxyl group, and proceeds with migration of the C3—C4 bond to give the A-homo-3-one III (R = OH). This is in direct contrast to the rearrangement of 5α-cholestan-3-one (I, R = C8H17), which...
Article
A survey of methods for the preparation of acid- and base-labile steroid Δ5-3-ketones showed that oxidation of the appropriate Δ5-3β-alcohols with dicyclohexylcarbodiimide–dimethyl sulfoxide (Moffatt reagent) was the most satisfactory, giving yields of 60–70% of the required ketones with little or no isomerization to the corresponding Δ4-3-ketones....
Article
The data presented substantiate the conclusions reported previously (1) regarding the applicability of the Hendrickson (2, 3) cycloheptane-based conformational analytical procedure to A-homosteroid-ketones of the 5α- and 5β- androstane and estrane series. For such cycloheptanone derivatives (with no bulky substituents at C-1 to C-5 of ring A) the t...
Article
As the first stage in the investigations of the mechanisms of action of carcinogenic lactones, the reactions of 4-hydroxypent-2-enoic acid lactone (II, R = CH3), which is a carcinogen, and of the non-carcinogenic 4-hydroxypent-3-enoic (III, R = CH3) and 4-hydroxypentanoic (IV, R = CH3) acid lactones with methylamine and benzylamine have been studie...
Article
Determination of the activation parameters for the acid-, base-, and enzyme-catalyzed isomerizations of androst-5-ene-3,17-dione has revealed that the facility of the enzymic process is mainly due to an extremely low enthalpy of activation of 5.0 kcal mole−1. Further circumstantial evidence regarding the nature of the reacting groups at the active...
Article
The synthesis of some potential nitrogen mustard precursor 17α-bis(2-hydroxyethyl)aminomethyl androst-17β-ol derivatives has been achieved by two routes. During the investigation, unequivocal proof was obtained that addition of cyanide to 17-keto steroids gives predominantly 17β-hydroxy-17α-cyano epimers.
Article
The difficulties which in the past have precluded the preparation of some synthetically potentially useful ethylenedioxy-tetrahydronaphthalenone and -dihydroindanone derivatives have been overcome. The proclivity of the tetrahydronaphthalenone compounds to undergo acid- and base-catalyzed rearrangements has been shown to be paralleled to some exten...
Article
The relative alkylating capabilities of crotyl chloride, allyl bromide, and 1-bromo-2-butyne with respect to compounds containing thiol, imidazole, primary amino, and methylthio functions representative of those present in cysteine, histidine, lysine and methionine residues have been studied using 2-bromoacetophenone as the reference alkylating age...
Article
The synthesis of cyclohexylidene derivatives by condensation of α-lithiocyclohexylphosphonic acid bis(dimethylamide) with some carbonyl compounds has been studied. The desired olefin was obtained when the carbonyl moiety was an aldehyde but, probably for steric reasons, not when ketones were used.
Article
Comparative studies on the reactions of cysteine, methionine, histidine, and lysine derivatives with allyl bromide, 1-bromo-2-butyne, and 2-bromoacetophenone have been carried out in connection with an evaluation of the potential of reagents incorporating ethylenic and acetylenic functions for protein modification.
Article
Studies on the acid-, base-, and enzyme-catalyzed isomerizations of several variously C-17 substituted Δ5-3-ketosteroids have indicated micellar aggregation of relatively non polar substrates in the dilute aqueous methanol assay solvent to be an important consideration when evaluating specificity data. Further evidence that the isomerase is sensiti...
Article
The diazomethane homologation of a broad spectrum of variously C-17-substituted steroid-3-ketones has shown that the C8H17 cholestane side chain exerts a unique influence on the direction of the ring enlargement reaction. This long-range effect is not explicable in terms of polar or conformational transmission.
Article
The Michael additions of α-toluenethiol, methylamine, and benzylamine to 4-hydroxypent-2-enoic acid lactone have been confirmed to be facile. The analogous additions of imidazole and glycine amide are much less readily accomplished and no stable Michael addition product could be detected with guanidine as the base. In the pH range 6–9, subsequent l...
Article
Studies on the reactions of carcinogenic γ-lactones and related compounds with analogues of guanine DNA residues indicate that the lactones themselves will not effect permanent alkylation of the guanine N-7 position since the Michael addition reactions involved would be readily reversible. In contrast, the α,β-unsaturated acids resulting from hydro...
Chapter
The invention of site-directed amino acid (AA) mutagenesis (1) has revolutionized the way in which enzyme mechanism and specificity can be probed, while simultaneously providing a route for engineering novel enzyme properties. Prior to this very precise method of AA replacement, protein chemists utilized chemical modification and chemical mutagenes...
Article
The continuing ability of bacteria to resist current antibiotic treatments highlights the need for alternative strategies for inhibiting their pathogenicity. Bacterial attachment is a major factor in infectivity and virulence. This key binding phase of bacteria to any potential host is mediated by adhesin proteins and so these present an attractive...
Article
Molecular angler fish: By precisely positioning different binding ligands (L) around the active site "mouth" of a degradative proteinase enzyme, target proteins (TP) can be plucked from solution, locked in position adjacent to the catalytic triad "jaws", and in this way readily and specifically degraded (see scheme). In this strategy, the appropria...
Article
The cover picture shows a ligand-targeted proteinase enzyme or “catalytic antagonist” acting as a molecular angler fish: By precisely positioning different binding ligands (L) around the active site “mouth” of a degradative proteinase enzyme, target proteins (TP) can be plucked from solution, locked in position adjacent to the catalytic triad “jaws...
Article
Preparation of chiral, nonracemic γ-lactones by enzymecatalyzed oxidation of meso-diols: ( + )-(1R,6S)-8-oxabicyclo[4.3.0]nonan-7-one
Article
Site-selective glycosylation at position 166 at the base of the primary specificity S1 pocket in the serine protease subtilisin Bacillus lentus (SBL) created glycoproteins that are capable of catalyzing the coupling reactions of not only L- amino acid esters but also D-amino acid esters to give the corresponding dipeptides in good yields as a...
Article
The strategy of combined site directed mutagenesis and chemical modification creates chemically modified mutants (CMMs) with greatly broadened substrate specificities. We have previously reported that the CMMs of subtilisin Bacillus lentus (SBL) are efficient catalysts for the coupling of both L-and D-amino acids. We now report that these powerful...
Article
Methanethiosulfonate reagents may be used to introduce virtually unlimited structural modifications in enzymes via reaction with the thiol group of cysteine. The covalent coupling of enantiomerically pure (R) and (S) chiral auxiliary methanethiosulfonate ligands to cysteine mutants of subtilisin Bacillus lentus induces spectacular changes in cataly...
Article
Using site directed mutagenesis combined with chemical modification, we have developed a general and versatile method for the glycosylation of proteins which is virtually unlimited in the scope of proteins and glycans that may be conjugated and in which the site of glycosylation and the nature of the introduced glycan can be carefully controlled. W...
Article
Glycoproteins occur naturally as complex mixtures of differently glycosylated forms which are difficult to separate. To explore their individual properties, there is a need for homogeneous sources of carbohydrate-protein conjugates and this has recently prompted us to develop a novel method for the site-selective glycosylation of proteins. The pote...
Article
Full-text available
Transition state analogue boronic acid inhibitors mimicking the structures and interactions of good penicillin substrates for the TEM-1 beta-lactamase of Escherchia coli were designed using graphic analyses based on the enzyme's 1.7 Angstrom crystallographic structure. The synthesis of two of these transition state analogues, (1R)-1-phenylacetamido...
Article
A transition state analogue inhibitor, boronic acid benzophenone (BBP) photoprobe, was used to study the differences in the topology of the S1 pocket of chemically modified mutant enzymes (CMMs). The BBP proved to be an effective competitive inhibitor and a revealing active site directed photoprobe of the CMMs of the serine protease subtilisin Baci...
Article
Twelve novel glycomethanethiosulfonate (glyco-MTS) protein glycosylation reagents have been prepared. Their use in a controlled site-selective glycosylation strategy that combines site-directed mutagenesis with chemical modification allows protein glycosylation with concomitant control of (i) site, (ii) carbohydrate, (iii) anomeric stereochemistry,...
Article
The use of methanethiosulfonates as thiol-specific modifying reagents in the strategy of combined site-directed mutagenesis and chemical modification allows virtually unlimited opportunities for creating new protein surface environments. As a consequence of our interest in electrostatic manipulation as a means of tailoring enzyme activity and speci...
Article
The use of methanethiosulfonates as thiol-specific modifying reagents in the strategy of combined site-directed mutagenesis and chemical modification allows virtually unlimited opportunities for creating new protein surface environments. As a consequence of our interest in electrostatic manipulation as a means of tailoring enzyme activity and speci...
Article
The synthesis of pure, well-defined glycoproteins is essential to the study of the host of biological processes that they mediate. The use of a combined site-directed mutagenesis and chemical modification strategy allows the site-selective synthesis of homogenous glycoproteins, the determination of precise structure-activity relationships and the d...
Article
The explosion in commercial and synthetic applications of enzymes has stimulated much of the interest in enhancing enzyme functionality and stability. Covalent chemical modification, the original method available for altering protein properties, has now re-emerged as a powerful complementary approach to site-directed mutagenesis and directed evolut...
Article
A series of chemically modified mutants (CMMs) of subtilisin B. lentus (SBL) were generated employing the combination of site-directed mutagenesis and chemical modification. This strategy entails the mutation of a selected active site residue to cysteine and its subsequent modification with a methanethiosulfonate reagent CH3SO2S-R, where R may be i...
Article
Employing the strategy of combined site directed mutagenesis and chemical modification, we previously generated chemically modified mutant enzymes (CMMs) of subtilisin Bacillus lentus (SBL). We now report the use of these SBL-CMMs for peptide coupling reactions. The SBL-CMMs exhibit dramatically altered substrate specificity, including the acceptan...
Article
For synthetic applications of proteases, such as for peptide coupling, a combination of high esterase and low amidase activities is required. While achieving such specificity has been a long-standing goal, the decreases in amidase activity achieved to date have often also been accompanied by decreases in esterase activity. In the current study, a s...
Article
A combined site-directed mutagenesis and chemical modification strategy has been used to create superior enzyme catalysts for the resolution of racemic primary and secondary alcohols using a transesterification reaction. The chemically modified mutant, N62C–S–CH3, of subtilisin Bacillus lentus catalyzes the transesterification of N-acetyl-L-phenyla...
Article
The reaction between methanethiosulfonate reagents and cysteine mutants of subtilisin is quantitative and can be used to prepare chemically modified mutant enzymes (CMMs) with novel properties. The virtually unrestricted structural variations possible for CMMs presents a preparative and screening challenge. To address this, a rapid combinatorial me...
Article
Developing the ability to vary the pH−activity profile of an enzyme in a controlled manner has been a long sought-after goal. Such tailoring provides important insights into mechanism and permits optimization of enzyme performance in organic synthesis applications. The most successful approaches to date toward altering pH−activity profiles of enzym...
Article
By combining site-directed mutagenesis with chemical modification, we have altered the S1 and S1' pocket specificity of subtilisin Bacillus lentus (SBL) through the incorporation of unnatural amino acid moieties, in the following manner: WT --> Cysmutant + H3CSO2SR --> Cys-SR, where R may be infinitely variable. A paradigm between extent of activit...
Article
Subtilisin Bacillus lentus catalyzes transesterifications between N-acetyl-L-phenylalanine vinyl ester and a wide range of alcohols. Reaction yields are high when primary alcohols are used, and quantitative with methanol. With chiral alcohols, the reaction is enantioselective, and the stereoselectivity is reversed on going from open chain secondary...
Article
In order to probe the structural basis of stereoselectivity in the serine protease family, a series of enantiomeric boronic acids RCH2CH(NHCOCH3)B(OH)2 has been synthesized and kinetically characterized as transition-state analog inhibitors using alpha-chymotrypsin and subtilisin Carlsberg as model systems. When the R-substituent in this series was...
Article
The capacities of subtilisin Carlsberg (SC) and α-chymotrypsin (CT), which are representative of synthetically useful serine proteases, to discriminate between R- and S-configurations of stereocenters remote from the catalytic site have been further explored using chiral naphthyl aldehyde transition state analog inhibitors as probes. The inhibitors...
Article
An efficient process utilizing a modified Curtius rearrangement was developed for the synthesis of carbamate substrates 1a-c and 2. The potential of these compounds as prodrug structures 3 for antibody-directed abzyme prodrug therapy (ADAPT) has been chemically evaluated.
Article
Peptidyl boronic acids that are close structural analogues of good substrates have been prepared and evaluated as potential transition state analogue inhibitors of the representative cysteine protease, papain. However, no inhibition could be detected at concentrations up to 10 mM. The reasons for the lack of inhibition were sought from molecular mo...
Article
The thiol side chain of the M222C mutant of the subtilisin from Bacillus lentus (SBL) has been chemically modified by methyl-, aminoethyl-, and sulfonatoethylthiosulfonate reagents. Introduction of charged residues into the active site of the enzyme reduced the catalytic efficiency with Suc-AAPF-pNA as the substrate, but resulted in better binding...
Article
Specificity differences between the S1-pockets of subtilisin B. lentus (SBL), and its M222C/S mutants have been explored with boronic acid inhibitors. Similar binding trends were noted, with 2,4-dichlorophenylboronic acid being the best overall inhibitor for each enzyme. In addition, a correlation between inhibitor binding and the electrophilicity...
Article
The structure of the plasmid-mediated beta-lactamase TEM-1 has been solved in complex with a designed boronic acid inhibitor (1R)-1-acetamido-2-(3-carboxyphenyl)ethane boronic acid at 1.7 A resolution. The boronate inhibitor was designed based on the crystallographic coordinates of the acyl-enzyme intermediate of TEM-1 bound to the substrate penici...
Article
Full-text available
Despite the widespread exploitation of enzymes for synthetic purposes in both academic and industrial applications, little is known about the factors that determine enzyme specificity. In view of the increasingly broad spectrum of unnatural substrate structures that synthetically useful enzymes are required to handle, it is becoming essential to de...
Article
Various enantiomeric amine and aminoalcohol amide and α-ketoamide derivatives have been evaluated as competitive inhibitors of the representative serine proteases α-chymotrypsin (CT) and subtilisin Carlsberg (SC). Each compound studied was an effective competitive inhibitor of both enzymes. However, only for the best inhibitor, N-pyruvoyl-1-(1-naph...
Article
Enantiomeric 1-acetamido boronic acids, which are N-acetyl transition state analog inhibitor analogs of l- and d-forms of the amino acids alanine, phenylalanine, p-fluorophenylalanine, p-chlorophenylalanine, and 1-naphthylalanine, have been evaluated as inhibitors of the serine proteases subtilisin Carlsberg (SC) and α-chymotrypsin (CT). All of the...
Article
The abilities of the synthetically useful serine proteases, subtilisin Carlsberg (SC) and α-chymotrypsin (CT), to discriminate between R- and S-configurations of stereocenters remote from the catalytic site have been explored using chiral aldehyde transition state analog inhibitors as probes. The inhibitors evaluated were (R)- and (S)-3-phenylbutan...
Article
The usefulness and practicality of enzymes as chiral catalysts in organic synthesis are now well documented, with their applications in creating enantiomerically pure synthons for the asymmetric synthesis of important natural products of academic and pharmaceutical interest being particularly important. Enzyme groups of proven value in this regard...
Article
(Z)-Heptadec-8-enylboronic acid, a potential lipase inhibitor that is isosteric with oleic acid, and that is unexpectedly sensitive to aerial oxidation, has been prepared in 23% overall yield from dec-1-yne and 7-bromoheptanol. Disappointingly, the target compound proved inactive under conditions where lipase inhibition would have been expected.
Article
The synthesis of (1R)-1-acetamido-2-(3-carboxyphenyl)ethane boronic acid , a rationally designed transition state analog competitive inhibitor of the RTEM-1 β-lactamase from Escherichia coli, is reported Kinetic measurements show that, as designed, it is a highly effective reversible inhibitor of the β-lactamase, with an inhibition constant of 110...
Article
Aziridine derivatives of E-64 have been synthesized, and their characterization against the cysteine proteases cathepsin B, cathepsin L, and papain is reported. The inhibition was found to be strongly pH-dependent, with maximum activity observed at pH 4, indicating that the protonated aziridinium ion form of the inhibitor is the more reactive form....
Article
L-N-Acetyl-O-(arylalkyl)-serines incorporating two stereocenters were prepared via ring-opening reactions of an aziridine precursor, derived from L-serine, with each of R and S 1-phenyl- and 2-methoxy-2-phenylethanol. These were than evaluated as inhibitors of the serine proteases subtilisin Carlsberg and α-chymotrypsin in order to probe the effect...
Article
The substrate specificities of L-alpha-hydroxy acid dehydrogenases, including L-lactate dehydrogenases (L-LDH's), can often be quite broad. However, an LDH with high catalytic activity toward alpha-keto acids with positively charged side chains, such as those containing ammonium groups, has not been described, even though there is evidence from met...
Article
The L-lactate dehydrogenase of Bacillus stearothermophilus (BSLDH) is a highly stereospecific enzyme that catalyzes synthetically useful reductions of 2-keto acids to the corresponding L-2-hydroxy acids. The strategy of probing the factors controlling enzyme stereospecificity by evaluating BSLDHs resistance to being induced to reverse its stereospe...
Article
Surface glycoproteins act as markers in cell-cell com-munication events that determine microbial virulence, 1 inflammation 2 and host immune responses. 3 In addition, the correct glycosylation of proteins is critical to their expression and folding 4 and increases their thermal and proteolytic stability. 5 Glycoproteins occur naturally in a number...
Article
Using the X-ray analyses of papain and papain-chloromethyl ketone inhibitor complexes as representative cysteine protease structures, molecular graphics analyses were applied to design (4R,1'S)-2-[1'-[(benzyloxycarbon)amino]ethyl]4-benzyl-4-[[(2-oxoethyl)amino]carbonyl]-3,4,5,6-tetrahydropyrimidine (1) as a conformationally restricted, competitive...
Article
Using bicyclononyl-, (adamantylmethyl)-, and biphenylmalonate substrate probes, the dimensions of the large hydrophobic pocket of the active site model of pig liver esterase have been established as 6.2 x 3.1 x 4.7 Angstrom(3). It is believed that the current refinement completes the basic specification of the active site model and that, for the ma...
Article
Inhibition constants for substituted phenyl and phenylethyl boronic acids have been determined. The trends and factors involved in their binding are discussed.