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. 1968 Nov;110(1):53-7.
doi: 10.1042/bj1100053.

Evidence for histidine in the active sites of ficin and stem-bromelain

S S Husain, G Lowe

Evidence for histidine in the active sites of ficin and stem-bromelain

S S Husain et al. Biochem J. 1968 Nov.

Abstract

1. Ficin and stem-bromelain are irreversibly inhibited by 1,3-dibromoacetone, a reagent designed to react first with the active-site cysteine residue and subsequently with a second nucleophile. Evidence is presented that establishes that a histidine residue is within a 5A locus of the active-site cysteine residue in both enzymes. The histidine residue in both enzymes is alkylated at N-1 by dibromoacetone. It is suggested that, as with papain, the thiol and imidazole groups act in concert in the hydrolysis of substrates by these enzymes. 2. The inhibition of thiol-subtilisin with 1,3-dibromoacetone is shown to be due to the alkylation of a cysteine residue only.

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References

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