Hydrolases, such as Pig Liver Esterase, are widely used in organic synthesis due to their low cost, stability, and ability to accept a wide range of substrates.  It is well known that PLE is composed of at least 6 isoenzymes, which have recently been recombinantly produced.  However, the role of each individual isoenzyme in the PLE mixture has not yet been explored completely.  It has been demonstrated that the addition of organic co-solvents to the phosphate buffer can dramatically alter the enantiomeric excess (ee) of the reaction.  We have found that the addition of just 2% EtOH into our buffer solution greatly increased the enantiomeric excess of compound (1)  from 23 %ee to 85 %ee.  Additionally, several of the isoenzymes (3-6) displayed a solvent induced inversion of chirality from the (S)-enantiomer to the (R)-enantiomer.  However, we have also found that this increase in enantioselectivity is highly substrate specific.  For example, addition of varying amount of co-solvent to compound (2)  showed only moderate increases in enantioselectivity, and addition of co-solvent to compound (3)  did not show any effect.  These results and the results of varying the isoenzymes with these substrates will be discussed in detail.

Investigation of cosolvent effects on the PLE hydrolysis reaction of several substrates using combined HPLC-MS techniques

243rd National Meeting (2012)

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