SPECIFICITY TO LEAVING GROUP IN TRANSESTERIFICATION OF SUBSTITUTED PHENYL-ESTERS IN ORGANIC-SOLVENTS CATALYZED BY SUBTILISIN MICROGEL SOLS

被引:4
作者
EVANS, DJ
WILLIAMS, A
ALCANTARA, AR
PRYCE, RJ
机构
[1] UNIV CANTERBURY,CHEM LAB,CANTERBURY CT2 7NH,ENGLAND
[2] UNIV COMPLUTENSE MADRID,FAC PHARM,DEPT ORGAN & PHARMACEUT CHEM,E-28040 MADRID,SPAIN
[3] SHELL RES LTD,SITTINGBOURNE RES CTR,SITTINGBOURNE ME9 8AG,KENT,ENGLAND
来源
JOURNAL OF MOLECULAR CATALYSIS | 1993年 / 81卷 / 01期
关键词
IMMOBILIZED ENZYME; MICROGELS; ORGANIC SOLVENTS; PHENYL ESTERS; SPECIFICITY; SUBTILISIN; TRANSESTERIFICATION;
D O I
10.1016/0304-5102(93)80026-Q
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Subtilisin has been conjugated to microgels possessing carboxyl functions. The effect of changing the leaving group on transesterification reactions of substituted phenyl acetate and hippurate esters catalysed by a subtilisin-microgel conjugate at pH 9.9 is shown to be governed by the following Bronsted equations (the pH is that of the stock enzyme-conjugate in water, added at a rate of 4% v/v to the organic solvent): log k(cat)/K(m) = -0.54 +/- 0.06 pK(a) + 6.92 +/- 0.53 (acetates, methanol) (i) log k(cat)/k(m) = -0.50 +/- 0.08 pK(a) + 7.23 +/- 0.65 (hippurates, methanol) (ii) log k(cat)/K(m) = -0.83 +/- 0.13 pK(a) + 9.95 +/- 1.1 (hippurates, butanol/acetonitrile at 16.7% v/v) (iii) The more negative slope (beta1g) for the butanol/acetonitrile composition is most likely due to a ground state effect on the effective charge on the esters. alpha-Chymotrypsin has been conjugated with microgels possessing primary amino comonomer components or sulphonic acid with carboxyl functions. The resultant enzyme-polymer conjugates exhibit good solubility properties in organic media over a wide range of pH for the stock aqueous solution of the conjugate. There is no diminution in activity of a solution of the subtilisin-microgel conjugate after 35 days compared with a drop of some 90% for the native enzyme over the same period under the same conditions.
引用
收藏
页码:119 / 131
页数:13
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