Steady-state kinetics of the oxidation of (S)-1-phenyl-1,2-ethanediol catalyzed by alcohol dehydrogenase from Candida parapsilosis CCTCC M203011

Kinetic studies of oxidation reaction of (S)-1-phenyl-1,2-ethanediol (PED) catalyzed by a NAD⁺-dependent alcohol dehydrogenase from Candida parapsilosis CCTCC M203011 obtained from China Center for Type Culture Collection (CPADH) were observed for getting insight into the deracemization redox reaction. The data of initial velocity experiments in the absence of product, product (β-hydroxy-hypnone) inhibition experiments and dead-end (pyrazole) inhibition experiments strongly suggest that the reaction follows Theorell-Chance BiBi mechanism in which the coenzymes bind to the free form of the enzyme firstly. The kinetic parameters of this model were estimated by using non-linear regression analysis software.     

Microbial deracemisation of aromatic β-hydroxy acid esters

Aromatic β-hydroxy acid esters were found to undergo deracemisation using whole cells of Candida parapsilosis. The conditions for the deracemisation reaction were optimised where 75% isolated yield and >95% enantiomeric excess of the product was achieved. The effect of electron donating as well as electron withdrawing groups present in the standard substrate, ethyl 3-hydroxy 3-phenyl propionate was studied to establish the generality of the reaction. The enantiomeric excess of the product remains high (>95%) irrespective of the different substituents in the para position but substitution at the ortho position obstructs the process. Similarly, ethyl and methyl esters of the standard substrate undergo deracemisation reaction giving high ee of the product, but the benzyl ester of the standard substrate did not undergo deracemisation.