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Abstract Background Use of enzymes in low water media is now widely used for synthesis and kinetic resolution of organic compounds. The frequently used enzyme form is the freeze-dried powders. It has been shown earlier that removal of water molecules from enzyme by rinsing with n-propanol gives preparation (PREP) which show higher activity in low water media. The present work evaluates PREP of the lipase (from Rhizomucor miehei) for kinetic resolution of (R,S)-β-citronellol. The acylating agent was vinyl acetate and the reaction was carried out in solvent free media. Results The PREP, with 0.75% (v/v, reaction media) water, was indeed found to be more efficient and gave 95% conversion to the ester. Using this PREP, with no added water, 90% ee for (R)-(+)-β-citronellyl acetate at 45% conversion (E = 42) was obtained in 4 h. The control with freeze-dried enzyme, with zero water content, gave 78% ee at 30% conversion (E = 13). FT-IR analysis showed that PREP had retained the α-helical content of the enzyme. On the other hand, freeze-dried enzyme showed considerable loss in the α-helical content. Conclusion The results show that PREP may be a superior biocatalyst for enantioselective conversion by enzymes in low-water media.

Reactions involving tert-alcohols and their esters are generally not catalyzed by lipases. Candida rugosa lipase is one of the few lipases which shows at least limited catalytic activity towards tert-alcohols and their esters. Using transesterification of tributyrin with tertiary butyl and amyl alcohols as a model reaction, it is shown that precipitation of lipase by a tertiary alcohol in the presence of a buffer with optimum concentration enhances the catalytic activity 7 fold as compared to rates obtained with lyophilized powders. Optimization of the ratio of triglyceride to tert-alcohols and medium engineering gave an initial rate which was 41 times higher than that obtained with lyophilized powders. Hence, use of a simple enzyme formulation, coupled with optimization of reaction conditions led to Candida rugosa lipase becoming a useful catalyst for catalyzing transesterification involving tertiary alcohols. [ABSTRACT FROM AUTHOR]

The structures of isoenzymes differ and yet these catalyse the same type of reaction. These structures evolved to suit the physiological needs and are located in different parts of cells or tissues. Moonlighting proteins represent the same structure performing verydifferent biological functions. Biological promiscuity reveals that the same active sites can catalyse different types of reactions. These three differentphenomena, all illustrate similar evolutionary strategies. Viewed together, it emerges that biologists need to take a hard look at the‘structure–function’ paradigm as well as the notions of biological specificity. Meanwhile, biotechnologists continue to exploit the opportunities which ‘non specificity’ offers. [ABSTRACT FROM AUTHOR]