Identification of a Functional Cysteine Essential for the Activity of Guinea Pig Liver Transglutaminase

Abstract

Inactivation of transglutaminase by 14C-iodoacetamide is accompanied by a proportional uptake of 14C-carbamidomethyl. Incorporation of 1 mole of this group per mole of enzyme results in complete inactivation. Proteolytic digestion of 14C-carbamidomethyl-labeled enzyme yields two related radioactive peptides containing the S-(14C-carbamidomethyl)cysteinyl residue. The amino acid sequences of these peptides have been determined as Gly-Gln-S-(carbamidomethyl)cysteine-Trp and Tyr-Gly-Gln-S-(carbamidomethyl)cysteine-Trp.