Cathepsin B (EC 3.4.22.1)

Abstract In 1941 Fruton and co-workers [1377] proposed a classification of the proteolytic enzymes of animal tissues in which they included an enzyme that hydrolysed Bz-Arg-NH2, a synthetic substrate of trypsin. At that time, this thiol-dependent enzyme was termed cathepsin II, but the nomenclature was further revised by Tallan et al. in 1952 [1401], who renamed cathepsin II as cathepsin B. Further characterization was done by Greenbaum and Fruton [1379]. Otto and co-workers, however, showed that two enzymes had contributed to the activity assigned to 'cathepsin B' in earlier work. Thus, gel filtration of enzymes from rat liver lysosomes separated components of 25 kDa and 52 kDa, both of which hydrolysed Bz-Arg-NH2. The 25 kDa endopeptidase was briefly known as cathepsin B' and cathepsin B1, but in reviewing this work in 1971, Otto [1272] termed the enzyme cathepsin BJ. The second enzyme (cathepsin B2) was a carboxypeptidase, and when this was renamed 'lysosomal cysteine-type carboxypeptidase' (EC 3.4.18.1), the original name of cathepsin B could be used once more for the endopeptidase. In 1972, the nomenclature committee of Inter national Union of Biochemistry (IUB) recommended the name cathepsin B, with the EC number 3.4.22.1. Cathepsin B appears to be ubiquitous in mammals, having been detected in nearly all organs and tissues. Also enzymes with similar properties occur in many lower organisms.