Nucleophile specificity in α-chymotrypsin- and subtilisin-(Bacillus subtilis strain 72) catalyzed reactions

• Nucleophilic properties of amino-acids were studied systematically in acyl-transfer reactions catalyzed by α-chymotrypsin and subtilisin from Bacillus subtilis strain 72 (subtilisin 72) using Mal-l-Ala-l-Ala-l-PheOMe as the acyl-group donor. In α-chymotrypsin-catalyzed reactions, the nucleophile reactivities increase in the following order: d-AlaNH2 < GlyNH2 < l-AlaNH2 < l-ScrNH2 < l-ThrNH2 < l-HisNH2 < l-ValNH2 < l-LcuNH2 < l-TrpNH2 < l-MetNH2 < l-NvaNH2 < l-PheNH2 < l-IleNH2 < l-TyrNH2 < l-ArgNH2. In reactions catalyzed by subtilisin 72, the reactivities increase as follows: l-LeuNH2 < l- IleNH2 < l-ThrNH2 < l-ArgNH2 < l-TrpNH2 < l-NvaNH2 < l-ValNH2 < l-MctNH2 < l-AlaNH2 < l-ScrNH2 < d-AlaNH2 < GlyNH2. In α-chymotrypsin-catalyzed reactions, hydrophobic interactions are entirely responsible for the differences between the reactivity of the nucleophiles for amides of all the amino-acids tested with the exception of d-AlaNH2, l-ArgNH2 and l-TyrNH2. In the reactions catalyzed by subtilisin 72, Amino-acid side-chain characteristics and the nucleophile reactivities are not related. The data obtained show the low selectivity of the S1′ subsite of subtilisin 72 and high specify of this subsite in α-chymotrypsin.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Industriell bioteknik -- Biokatalys och enzymteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Industrial Biotechnology -- Biocatalysis and Enzyme Technology (hsv//eng)

Nyckelord

Nucleophile specificity

Quantitative structure activity relationship

Substrate specificity

Subtilisin

α-chymotrypsin

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