Rabbit liver transglutaminase: physical, chemical, and catalytic properties

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Abstract
Transglutaminase (R-glutaminyl-peptide:amine .alpha.-glutamyl-yltransferase [EC 2.3.2.13]) was purified to apparent homogeneity from extracts of rabbit liver. The enzyme is a single polypeptide chain of approximately 80,000 MW containing 1 catalytic site per molecule. That the isolated enzyme is the rabbit counterpart of the well-characterized guinea pig liver transglutaminase is evidenced by the similarities in their amino acid compositions and in their enzymic activities toward several substrates, together with the fact that the isolated rabbit enzyme is immunologically distinct from both rabbit plasma and rabbit platelet blood coagulation factor XIII. A striking difference between the catalytic activities of the rabbit and guinea pig enzymes is the low activity of rabbit transglutaminase for hydroxylamine incorporation into benzyloxycarbonyl-L-glutaminylglycine, a reaction for which the guinea pig enzyme shows a high reactivity. This finding reveals the cause of error in an earlier report that rabbit liver contains little, if any, of the enzyme. Preparation of, and analytical data on, several glutamine-containing peptide derivatives used in this study are reported here.