Location of the Essential Thiol of Porcine Liver Cathepsin B
- 1 January 1980
- journal article
- research article
- Published by Oxford University Press (OUP) in The Journal of Biochemistry
- Vol. 87 (1) , 347-350
- https://doi.org/10.1093/oxfordjournals.jbchem.a132744
Abstract
Porcine liver cathepsin B, a thiol enzyme, exists in at least three forms. While Form III is a single chain polypeptide, two peptide chains with molecular weights of 25,000 and 4,000 are noncovalently bound together in Form I and Form II. The present study showed that aminoterminal sequences of Form III and the 4,000-dalton peptide isolated from Form II are identical. The 4,000-dalton peptide contained three cysteine or half-cystine residues, one of which was demonstrated to be essential for the enzyme activity by an incorporation study with [14C]iodoacetate. It was also shown that the 4,000-dalton peptide of the activated enzyme contained one cysteine and one cystine residue.Keywords
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