Premium
Enzymes in preparative organic synthesis: Coincidence of the pH optimum for catalyst effectiveness with the pH optimum for the catalyzed reaction equilibrium
Author(s) -
Martinek Karel,
Semenov Anatole N.,
Berezin Ilya V.
Publication year - 1981
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.260230518
Subject(s) - chemistry , catalysis , reagent , equilibrium constant , chloroform , ionic strength , aqueous solution , aqueous two phase system , enzyme catalysis , organic chemistry , inorganic chemistry
The study concerned the pH profile of the apparent equilibrium constant for synthesis of N ‐benzoyl‐ L ‐phenylalanine ethyl ester from the respective acid and ethanol in the biphasic system chloroform + 5% (v/v) water. The substitution of water (as a reaction medium) for the biphasic aqueous–organic system shifted the pH profile toward neutral pH values. As a result the pH range thermodynamically conducive to synthesis of the final product in the biphasic system coincided with the pH optimum of the catalytic activity of the enzyme used (α‐chymotrypsin). This approach should, in principle, be considered as general: first, per se it is independent of a catalyst (enzyme) nature; second, the biphasic method helps the shift ionic equilibria involving not only organic acids, but also bases. A physical mechanism of the ionic equilibrium shift is the same is both cases, namely, a preferable extraction from water into an organic phase of one generally nonionic (more hydrophobic) form of the reagent.