Lipase catalysed synthesis of peptides: Preparation of a penicillin G precursor and other peptides

Enzymatic synthesis of amide surfactants from ethanolamine

The condensation of a primary amine with fatty acids has been studied to determine optimum conditions for selective formation of amide surfactants via enzymatic amidification. Monoacylated ethanolamide and the diacylated amide-ester can be isolated from the reaction mixture, but the monoacylated ester cannot be isolated. The selectivity of the reaction depends on the solubility of the intermediate amide. Continuous precipitation of this product decreases the amount of amide-ester produced. Solubility values of the desired product (amide) are reported for different conditions.In acetonitrile, the ethyl ester of the corresponding fatty acid has been used successfully to avoid formation/precipitation of the ion-pair of the precursor reagents. In this medium, use of the transacylation reaction permits one to accelerate the reaction without producing a significant change in the selectivity toward the intermediate amide. This strategy is not successful in n-hexane where the solubilities of both ethanolamine and its ion-pair with lauric acid are similar.Results obtained for high loadings of substrates have been analyzed. In n-hexane and acetonitrile, the kinetics of the direct acylation reactions are controlled by the limited solubility of the ion pair formed by the two precursor reagents For the transacylation reaction in acetonitrile, at a sustrate loading of 2 mol l(-1,) selective production of as much as 92 mole percent N-acyl ethanolamine was observed in only 1.5 h.

Effect of culture conditions on lipolytic enzyme production by Penicillium candidum in a solid state fermentation

Lipolytic enzymes were produced using wheat bran as substrate in a solid state fermentation with Penicillium candidum. The best production of lipolytic activity occurred at 29 degrees C. One hundred micromoles of free butyric acid (FBA) was released from tributyrin by 1 mL of cell free supernatant in the absence of control of environmental relative humidity. When a closed chamber saturated with water vapour was used the lipolytic activity increased to 320 micromoles of free butyric acid. The best initial reaction pH was 7.0. The highest activity, 480 micromoles of FBA, was obtained at a moisture content of 67.5 % of saturation.

Enzyme function in organic solvents

Enzyme catalysis in organic solvents is being increasingly used for a variety of applications. Of special interest are the cases in which the medium is predominantly non-aqueous and contains little water. A display of enzyme activity, even in anhydrous solvents (water less than 0.02% by vol.), perhaps reflects that the minimum necessity for water is for forming bonds with polar amino acids on the enzyme surface. The rigidity of enzyme structure at such low water content results in novel substrate specificities, pH memory and the possibility of techniques such as molecular imprinting. Limited data indicates that, while enhanced thermal stability invariably results, the optimum temperature for catalysis may not change. If true in general, this enhanced thermostability would have extremely limited benefits. Medium engineering and biocatalyst engineering are relevant techniques to improve the efficiency and stability of enzymes in such low water systems. Most promising, as part of the latter, is the technique of protein engineering. Finally, this review provides illustrations of applications of such systems in the diverse areas of organic synthesis, analysis and polymer chemistry.

Catalytic antibodies with lipase activity and R or S substrate selectivity

The specific hydrolysis of unactivated esters bearing an R or S enantiomeric alcohol has been achieved by two separate classes of catalytic antibodies induced to bind either the R or S substrates. The antibodies exhibit rate accelerations (10(3) to 10(5] above background hydrolysis that, coupled with their antipodal specificity, provide a novel set of reagents for use in synthesis.