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. 1979 Nov 1;183(2):369–373. doi: 10.1042/bj1830369

Evidence for association-activation effects in reactions of papain from studies on its reactivity towards isomeric two-protonic-state reactivity probes.

K Brocklehurst, J A Herbert, R Norris, H Suschitzky
PMCID: PMC1161567  PMID: 534503

Abstract

4-(N-Aminoethyl 4-pyridyl disulphide)-7-nitrobenzo-2-oxa-1,3-diazole was synthesized and evaluted as a two-protonic-state reactivity probe by kinetic study of its reactions with papain (EC 3.4.22.2) and with benzimidazol-2-ylmethanethiol. Evidence is presented to suggest that: (i) both this probe molecule and its 2-pyridyl isomer bind to papain; (ii) the binding is followed by a change in the environment of the thiol group of cysteine-25; (iii) the striking rate maximum in neutral media observed in the reaction of papain with the 2-pyridyl isomer but not with the 4-pyridyl isomer arises from association of the 2-pyridyl leaving group with the imidazolium ion of histidine-159.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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