Temperature-dependences of the kinetics of reactions of papain and actinidin with a series of reactivity probes differing in key molecular recognition features

Gul, S; Mellor, GW; Thomas, EW; Brocklehurst, K

Abstract

The temperature-dependences of the second-order rate constants (k) of the reactions of the catalytic site thiol groups of two cysteine peptidases papain (EC 3.4.22.2) and actinidin (EC 3.4.22.14) with a series of seven 2-pyridyl disulphide reactivity probes (R-S-S-2-Py, in which R provides variation in recognition features) were determined at pH 6.7 at temperatures in the range 4–30 °C by stopped-flow methodology and were used to calculate values of ΔS‡, ΔH‡ and ΔG‡. The marked changes in ΔS‡ from negative to positive in the papain reactions consequent on provision of increase in the opportunities for key non-covalent recognition interactions may implicate microsite desolvation in binding site–catalytic site signalling to provide a catalytically relevant transition state. The substantially different behaviour of actinidin including apparent masking of changes in ΔH‡ by an endothermic conformational change suggests a difference in mechanism involving kinetically significant conformational change.

Citation

Gul, S., Mellor, G., Thomas, E., & Brocklehurst, K. (2006). Temperature-dependences of the kinetics of reactions of papain and actinidin with a series of reactivity probes differing in key molecular recognition features. Biochemical Journal, 396(1), 17-21. https://doi.org/10.1042/BJ20051501

• Journal Article Type: Article
• Publication Date: May 15, 2006
• Deposit Date: Aug 8, 2007
• Journal: Biochemical Journal
• Print ISSN: 0264-6021
• Publisher: Portland Press
• Peer Reviewed: Peer Reviewed
• Volume: 396
• Issue: 1
• Pages: 17-21
• DOI: https://doi.org/10.1042/BJ20051501
• Keywords: Actinidin, activation parameter, conformational change, microsite desolvation, papain, temperature-dependence
• Publisher URL: http://dx.doi.org/10.1042/BJ20051501