Molecular dynamics simulations and electrostatic potential calculations were used to study the structure of a Rhizomucor miehei lipase (RmL)–substrate complex in a lipase catalyzed polyester synthesis. Two lipase–substrate complexes were constructed with sebacic acid and 1,4-butyl sebacate as substrates, energy minimized, and simulated for 100 ps. During the simulation, catalytically important hydrogen bonds were formed more easily, when the acid was placed in the hydrophobic end and the ester in the hydrophilic end of the active centre. However, also the polarity of the active centre amino acids probably affects the placement of the substrates. The electrostatic potential calculations showed significant differences in the electrostatic potential of the surface of RmL. This may help the lipase to orientate itself appropriately for the interfacial reaction.
[Show abstract][Hide abstract] ABSTRACT: The interest in the applications of biocatalysis in organic syntheses has rapidly increased. In this context, lipases have recently become one of the most studied groups of enzymes. We have demonstrated that lipases can be used as biocatalyst in the production of useful biodegradable compounds. A number of examples are given. 1-Butyl oleate was produced by direct esterification of butanol and oleic acid to decrease the viscosity of biodiesel in winter use. Enzymic alcoholysis of vegetable oils without additional organic solvent has been little investigated. We have shown that a mixture of 2-ethyl-1-hexyl esters can be obtained in a good yield by enzymic transesterification from rapeseed oil fatty acids for use as a solvent. Trimethylolpropane esters were also similarly synthesized as lubricants. Finally, the discovery that lipases can also catalyze ester syntheses and transesterification reactions in organic solvent systems has opened up the possibility of enzyme catalyzed production of biodegradable polyesters. In direct polyesterification of 1,4-butanediol and sebacic acid, polyesters with a mass average molar mass of the order of 56,000 g mol-1 or higher, and a maximum molar mass of about 130,000 g mol-1 were also obtained by using lipase as biocatalyst. Finally, we have demonstrated that also aromatic polyesters can be synthesized by lipase biocatalysis, a higher than 50,000 g mol-1 mass average molar mass of poly(1,6-hexanediyl isophthalate) as an example.
Journal of Biotechnology 12/1998; 66(1):41-50. DOI:10.1016/S0168-1656(98)00155-2 · 2.87 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The lipase from Rhizomucor miehei (formerly Mucor miehei) (RML) is a commercially available enzyme in both soluble and immobilized form with very high activity and good stability under diverse conditions (anhydrous organic solvents, supercritical fluids, etc.). Although this lipase was initially produced to be used in food industry, in this review we will focus our attention on the application of this enzyme in organic chemistry, from biodiesel production to fine chemicals (mainly in enantio or regioselective or specific processes). After showing the enzyme features, some of the most efficient methods of RML immobilization will be commented (entrapping on reverse micelles, preparation of cross-linked RML aggregates or immobilization on pre-existing solids). Finally, the main uses of the enzyme in organic chemistry will be revised. The use of RML in the production of biodiesel will be analyzed, and compared to the performance of other lipases. The synthesis of esters of carboxylic acids as flavors is other example where RML has been successfully employed. Taking advantage of the wide specificity of the enzyme, mainly a high enantiospecificity, many examples of the use of RML in the resolution of racemic mixtures of chiral carboxylic acids, alcohols or esters will be presented. Special mention requires the use of the regioselectivity of RML, mainly the chemistry of sugars. Finally, more unusual uses of RML will be presented (anomalous substrates, novel uses, etc.). In general, this enzyme seems very adequate for esterification reactions due to its high stability in anhydrous media and good esterification activity.
Journal of Molecular Catalysis B Enzymatic 06/2010; 64(1-2-64):1-22. DOI:10.1016/j.molcatb.2010.02.003 · 2.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Candida antarctica lipase B (CALB) is an established biocatalyst for a variety of transesterification, amidation, and polymerization reactions. In contrast to polyesters, polyamides are not yet generally accessible via enzymatic polymerization. In this regard, an enzyme-catalyzed ring-opening polymerization of β-lactam (2-azetidinone) using CALB is the first example of an enzymatic polyamide formation yielding unbranched poly(β-alanine), nylon 3. The performance of this polymerization, however, is poor, considering the maximum chain length of 18 monomer units with an average length of 8, and the molecular basis of the reaction so far is not understood. We have employed molecular modeling techniques using docking tools, molecular dynamics, and QM/MM procedures to gain insight into the mechanistic details of the various reaction steps involved. As a result, we propose a catalytic cycle for the oligomerization of β-lactam that rationalizes the activation of the monomer, the chain elongation by additional β-lactam molecules, and the termination of the polymer chain. In addition, the processes leading to a premature chain termination are studied. Particularly, the QM/MM calculation enables an atomistic description of all eight steps involved in the catalytic cycle, which features an in situ-generated β-alanine as the elongating monomer and which is compatible with the experimental findings.Keywords: Candida antarctica lipase B; enzyme catalysis; β-lactam ring-opening; molecular modeling; enzymatic polymerization; enzyme acylation
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