Molecular cloning and primary structure of Thermoactinomyces vulgaris carboxypeptidase T A metalloenzyme endowed with dual substrate specificity

A gene coding for an extracellular Zn-carboxypeptidase of Thermoactinomyces vulgaris has been cloned and sequenced (EMBL X56901). This enzyme named carboxypeptidase T reveals simultaneously both types of substrate specificity characteristic of mammalian carboxypeptidases A and B. The carboxypeptidase T gene is primarily expressed in E. coli as a non-active preproenzyme with an additional 98 amino acid residues at the N-terminus. Primary structure alignment or mature carboxypeptidase T and mammalian metallocarboxypeptidases demonstrated 25–30% overall identity but a full preservation of presumed catalytically important residues. These observations imply a basic uniformity of the general catalytic mechanism for enzymes of that class produced by evolutionarily remote organisms.