[Show abstract][Hide abstract] ABSTRACT: 1. A soluble D-alanine carboxypeptidase from Escherichia coli strain B was purified on a p-aminobenzylpenicillin-Sepharose column. This one-step chromatography followed by an (NH4)2SO4 precipitation yielded an enzyme purified 1200-fold and some of its properties are reported. 2. The pure D-alanine carboxypeptidase was devoid of D-alanine carboxypeptidase II activity and migrated as a single protein band on analytical disc gel electrophoresis. 3. Triton X-100 in the purification procedure is an absolute requirement for obtaining a stable enzyme. 4. The enzymic activity of D-alanine carboxypeptidase was greatly affected in solution of high salt concentrations and varied somewhat with the nature of the cation tested.
[Show abstract][Hide abstract] ABSTRACT: Studies were undertaken, using the isolated perfused rat heart, into various aspects of anoxia-induced enzyme release from the potassium arrested myocardium. Profiles for release, over periods of up to 8 h anoxia, were obtained for protein, creatine phosphokinase, myokinase, glutamate oxaloacetate transaminase, glyceraldehyde-3-phosphate dehydrogenase and α-hydroxybutyrate dehydrogenase. Two distinct peaks of enzyme release were observed; phase 1 release, which occurred during the first 10 to 60 min of anoxia and phase 2 release which followed phase 1 release and lasted for at least 7 to 8 h. In phase 1, 2 to 5% of the enzyme was released. Reoxygenation of the heart during phase 1 had a marginal effect upon overall enzyme release. Reoxygenation during phase 2 of enzyme release resulted in an immediate and massive increase in the rate of protein and enzyme release from the myocardium.
Journal of Molecular and Cellular Cardiology 09/1973; 5(4):395-407. · 5.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: High-yielding strains of Claviceps purpurea (Fr.) Tul, grown on a defined medium, have been used for a study of the biosynthesis of the peptide ergot alkaloid, ergotamine. l-[U-(14)C]tryptophan, dl-[2-(14)C]mevalonic acid lactone, sodium [2-(14)C]acetate, sodium [(14)C]formate and the methyl group of l-[methyl-(14)C]methionine were efficiently incorporated into the peptide alkaloids and specifically labelled the ergoline moiety of ergotamine. These results are the same as previously found for the biosynthesis of other ergot alkaloids. Time-course incubation experiments demonstrated that l-[U-(14)C]phenylalanine, l-[U-(14)C]proline and l-[U-(14)C]alanine were incorporated into the peptide ergot alkaloids. Chemical degradation of the radioactive alkaloid derived from additional precursor incubation experiments showed that phenylalanine and proline function as the most efficient precursors, and specifically label the constitutive side-chain phenylalanyl and prolyl moieties of the alkaloid. The evidence obtained from l-[U-(14)C]alanine-incorporation experiments was inconclusive. However, degradation of ergotamine isolated after incubation with dl-[1-(14)C]alanine, showed that the carboxyl group of the labelled amino acid was specifically incorporated into the alpha-hydroxy-alpha-amino acid residue of the alkaloid. This, in conjunction with the l-[U-(14)C]alanine-incorporation results, showed conclusively that all three carbon atoms of alanine were incorporated as a biosynthetic unit into the alpha-hydroxy-alpha-amino acid moiety of ergotamine.
[Show abstract][Hide abstract] ABSTRACT: In the absence of glucose, insulin stimulated the incorporation of (14)C-labelled amino acids into protein by perfused rat hearts that had been previously substantially depleted of endogenous glucose, glucose 6-phosphate and glycogen by substrate-free perfusion. This stimulation was also demonstrated in hearts perfused with buffer containing 2-deoxy-d-glucose, an inhibitor of glucose utilization. It is concluded that insulin exerts an effect on protein synthesis independent of its action on glucose metabolism. Streptozotocin-induced diabetes was found to have no effect either on (14)C-labelled amino acid incorporation by the perfused heart or on the polyribosome profile and amino acid-incorporating activity of polyribosomes prepared from the non-perfused hearts of these insulin-deficient rats, which show marked abnormalities in glucose metabolism. Protein synthesis was not diminished in the perfused hearts from rats treated with anti-insulin antiserum. The significance of these findings is discussed in relation to the reported effects of insulin deficiency on protein synthesis in skeletal muscle.
[Show abstract][Hide abstract] ABSTRACT: Studies with the isolated perfused working rat heart were carried out to investigate factors that may enable the heart to recover after periods of anoxia. It was found that the presence of glucose in the perfusion fluid during anoxia was essential for complete post-anoxic recovery and the presence of a high concentration of K(+) increased not only the rate of recovery but also the final extent of recovery. In an attempt to clarify the roles played by glucose and K(+) in aiding the survival and recovery of the anoxic myocardium the concentrations of parameters associated with energy liberation and anaerobic glycolysis (ATP, ADP, AMP, P(i), creatine phosphate, glycogen and lactate) were measured in the presence and absence of glucose during the anoxic phase. Determinations of these parameters were carried out during the working aerobic control period, the anoxic period (K(+) arrest) and the recovery period. The results demonstrated that glucose acted as an energy source during anoxia and thus maintained myocardial concentrations of high-energy phosphates, particularly ATP. These studies have also shown a direct relationship between the ability of the heart to recover and the concentration of myocardial ATP at the time of reoxygenation.
[Show abstract][Hide abstract] ABSTRACT: THE antagonistic effects of Pseudomonas fluorescens were first recorded by Garre1 in 1887. Several reports since have dealt with the biological activity of cultures and extracts of P. fluorescens2. We wish to report the production and purification of these inhibitory substances and the characterization of a metabolite responsible for a significant proportion of the antibacterial activity.
[Show abstract][Hide abstract] ABSTRACT: 1. The metabolism of glucose 6-phosphate in rat cerebral-cortex slices in vitro was compared with that of glucose. It was found that a glucose 6-phosphate concentration of 25mm was required to achieve maximal oxygen uptake rates and ATP concentrations, whereas only 2mm-glucose was required. 2. When 25mm-[U-(14)C]glucose 6-phosphate was used as substrate, the pattern of labelling of metabolites was found to be quantitatively and qualitatively similar to the pattern found with 10mm-[U-(14)C]glucose, except that incorporation into [(14)C]lactate was decreased, and significant amounts of [(14)C]glucose and [(14)C]mannose phosphate and [(14)C]fructose phosphate were formed. 3. Unlabelled glucose (10mm) caused a tenfold decrease in the incorporation of 25mm-[U-(14)C]glucose 6-phosphate into all metabolites except [(14)C]glucose and [(14)C]mannose phosphate and [(14)C]fructose phosphate. In contrast, unlabelled glucose 6-phosphate (25mm) had no effect on the metabolism of 10mm-[U-(14)C]glucose other than to increase markedly the incorporation into, and amount of, [(14)C]lactate, the specific radioactivity of this compound remaining approximately the same. 4. The effect of glucose 6-phosphate in increasing lactate formation from glucose was found to occur also with a number of other phosphate esters and with inorganic phosphate. Further investigation indicated that the effect was probably due to binding of medium calcium by the phosphate moiety, thereby de-inhibiting glucose uptake. 5. Incubations carried out in a high-phosphate high-potassium medium gave a pattern of metabolism similar to that found when slices were subjected to depolarizing conditions. Tris-buffered medium gave similar results to bicarbonate-buffered saline, except that it allowed much less lactate formation from glucose. 6. Part of the glucose formed from glucose 6-phosphate was extracellular and was produced at a rate of 12mumol/h per g of tissue in Krebs tris medium when glycolysis was blocked. The amount formed was much less when 25mm-P(i) or 26mm-HCO(3) (-) was present, the latter being in the absence of tris. 7. Glucose 6-phosphate also gave rise to an intracellular glucose pool, whereas no intracellular glucose was detectable when glucose was the substrate.
[Show abstract][Hide abstract] ABSTRACT: 1. The metabolism of [U-(14)C]glucose in perfused resting and contracting diaphragm muscle from normal rats and rats made diabetic with streptozotocin was studied in the presence and absence of insulin. 2. The incorporation of [U-(14)C]-glucose into glycogen and oligosaccharides was stimulated by insulin under all experimental conditions studied. 3. In the normal perfused resting diaphragm muscle the incorporation of radioactivity from [(14)C]glucose into lactate and CO(2) was not affected by insulin. 4. Periodic contractions, induced by electrical stimulation of the perfused diaphragm muscle in the absence of insulin, caused an increased incorporation of (14)C into glycogen and hexose phosphate esters, whereas incorporation of (14)C into lactate was greatly decreased. Production of (14)CO(2) in the contracting muscle was not significantly different from that in resting muscle. Addition of insulin to the perfusion liquid caused a further increase in formation of [(14)C]-glycogen in contracting muscle to values reached in the resting muscle in the presence of insulin. Formation of [(14)C]lactate was also stimulated by insulin, to values close to those found in the resting muscle in the presence of insulin. 5. In the diabetic resting muscle the rate of glucose metabolism was very low in the absence of insulin. Insulin increased formation of [(14)C]glycogen to the value found in normal muscle in the absence of insulin. Production of (14)CO(2) and formation of [(14)C]hexose phosphate remained unchanged. 6. In the diabetic contracting muscle production of (14)CO(2) was increased to values approaching those found in normal contracting muscle. Formation of [(14)C]lactate and [(14)C]glycogen was also increased by contraction, to normal values. Only traces of [(14)C]hexose phosphate were detectable. Addition of insulin to the perfusion medium stimulated formation of [(14)C]glycogen, to values found in normal contracting muscle. Production of [(14)C]hexose phosphate was stimulated by insulin, to approximately the values found in the normal contracting muscle. Production of (14)CO(2) and [(14)C]lactate, however, was not significantly affected by insulin. 7. These results indicate that the defects of glucose metabolism observed in perfused resting diabetic diaphragm muscle can be partially corrected by contraction, and in the presence of insulin the contracting diabetic muscle has a completely normal pattern of glycogen synthesis and lactate production, but CO(2) production remains impaired.
[Show abstract][Hide abstract] ABSTRACT: Fusicoccin is a non-specific phytotoxin. Variation in the response of the 75 plant species tested parallels their natural resistance to desiccation. Fusicoccin is effective when supplied via the sap stream but the wilt it produces is not caused by interruption of vascular flow. It penetrates undamaged plant surfaces very slowly. Fusicoccin, at high concentration, inhibits growth of seedlings in submerged culture but the effects disappear on transfer to fusicoccin-free media. The compound itself does not cause death of the cells and it does not destroy their semipermeability, as shown by the wilt's being reversible. Fusicoccin increases the susceptibility of a tissue to death by desiccation, and its precise site and mode of action remain obscure.Ophiobolins A and B destroy cell semi-permiability. Although they bear a close structural similarity to the fusicoccins the two groups have different modes of action.Progressive de-acetylation of fusicoccin reduces the degree of physiological activity as a wilting agent, but tomato shoots showed a novel response, involving an increase of fresh weight, after taking up small amounts of desacetyl-desisopentenyl fusicoccin.Some proposed mechanisms concerning the mode of action of fusicoccins are discussed.