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Altering lipase activity and enantioselectivity in organic media using organo‐soluble bases: Implication for rate‐limiting proton transfer in acylation step
Author(s) -
Chen ChunChi,
Chen TehLiang,
Tsai ShauWei
Publication year - 2006
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.20790
Subject(s) - chemistry , acylation , tetrahedral carbonyl addition compound , triethylamine , lipase , enzyme , hydrolysis , kinetic resolution , stereochemistry , organic chemistry , rate determining step , enantioselective synthesis , catalysis , nucleophile
Abstract With the hydrolytic resolution of ( R,S )‐naproxen 2,2,2‐trifluoroethyl esters via a partially purified papaya lipase (PCPL) in water‐saturated isooctane as the model system, the enzyme activity, and enantioselectivty is altered by adding a variety of organo‐soluble bases that act as either enzyme activators (i.e., TEA, MP, TOA, DPA, PY, and DMA) or enzyme inhibitors (i.e., PDP, DMAP, and PP). Triethylamine (TEA) is selected as the best enzyme activator as 2.24‐fold increase of the initial rate for the ( S )‐ester is obtained when adding 120 mM of the base. By using an expanded Michaelis–Menten mechanism for the acylation step, the kinetic analysis indicates that the proton transfer for the breakdown of tetrahedral intermediates to acyl‐enzyme intermediates is the rate‐limiting step, or more sensitive than that for the formation of tetrahedral intermediates when the enzyme activators of different pK a are added. However, no correlation for the proton transfers in the acylation step is found when adding the bases acting as enzyme deactivators. © 2006 Wiley Periodicals, Inc.