Partial purification and specificity of an arginine-converting enzyme from bovine epidermis

An enzyme which catalyzes the conversion of intraprotein arginine residue to intraprotein citrulline residue is present in bovine snout epidermis. This arginine-converting enzyme has been partially purified by (NH4)2SO4 preciptation chromatography on DEAE-cellulose and chromatography on Sephadex G-200. The enzyme is active at neutral pH, requires Ca2+ and a reducing agent and has an apparent molecular weight of 69 000. Its substrates include histone, polyarginine, S-carboxymethyl cysteine-hair keratin, S-carboxymethyl cysteine epidermal keratin and prekeratin and S-carboxymethyl cysteine-trichohyalin. A large number of proteins, synthetic and naturally occurring peptides, and other guanidine-containing compounds were substrates of the arginine-converting enzyme.