Subsite substrate specificity of midgut insect chymotrypsins

Subsite substrate specificity of midgut insect chymotrypsins

Author Sato, P. M. Google Scholar
Lopes, A. R. Google Scholar
Juliano, L. Autor UNIFESP Google Scholar
Juliano, M. A. Autor UNIFESP Google Scholar
Terra, W. R. Google Scholar
Institution Universidade de São Paulo (USP)
Universidade Federal de São Paulo (UNIFESP)
Abstract Insect chymotrypsins are distinctively sensitive to plant protein inhibitors, suggesting that they differ in subsite architecture and hence in substrate specificities. Purified digestive chymotrypsins from insects of three different orders were assayed with internally quenched fluorescent oligopeptides with three different amino acids at P1 (Tyr, Phe, and Leu) and 13 amino acid replacements in positions P1', P2, and P3. the binding energy (Delta G(s), calculated from Km values) and the activation energy (Delta G(T)(double dagger), determined from k(cat)/K-m values) were calculated. the hydrophobicities of each subsite were calculated from the efficiency of hydrolysis of the different amino acid replacements at that subsite. the results showed that except for S1, the other subsites (S2, S3, and S1') vary among chymotrypsins. This result contrasts with insect trypsin data that revealed a trend along evolution, putatively associated with resistance to plant inhibitors. in spite of those differences, the data suggested that in lepidopteran chymotrypsins S2 and S1' bind the substrate ground state, whereas only S1' binds the transition state, supporting aspects of the present accepted mechanism of catalysis. 2008 Elsevier B.V. All rights reserved.
Keywords subsites
substrate specificities
Language English
Date 2008-06-01
Published in Insect Biochemistry and Molecular Biology. Oxford: Pergamon-Elsevier B.V., v. 38, n. 6, p. 628-633, 2008.
ISSN 0965-1748 (Sherpa/Romeo, impact factor)
Publisher Elsevier B.V.
Extent 628-633
Access rights Closed access
Type Article
Web of Science ID WOS:000257002900003

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