Partial purification and characterization of cysteine proteinases in eccrine sweat

Attempts were made to purify and characterize cysteine proteinases in human eccrine sweat and further clarify their origin. Benzoyl-DL-arginine-beta-naphthylamide (BANA) and L-leucine beta-naphthylamide (LeuNA) hydrolases in thermally induced sweat were sequentially purified by Sephacryl S-200 chromatography and chromatofocusing, which yielded two major peaks of BANA hydrolase activity, BANA-I and BANA-II. Both enzymes are cysteine proteinases as evidenced by stimulation of enzymic activity by dithiothreitol and ethylenediaminetetraacetic acid and its inhibition by iodoacetic acid, (PCMB), and trans-epoxysuccinyl-L-leucylamido-(4-guanidino)-butane (E-64). Unlike BANA-II, BANA-I showed an additional aminopeptidase activity, an affinity to concanavalin A-Sepharose but no affinity to organomercurial sepharose and failed to hydrolyze benzyloxycarbonyl-phenylalanyl-arginine 4-methyl 7-coumarylamide (Z-Phe-Arg-NMec), a specific substrate for cathepsin B, which is poorly sensitive to leupeptin [inhibitor constant (Ki) = 1 X 10(-5) M] and relatively heat resistant. These and other characteristics such as its isoelectric points (PI) (= 5.8) and the Km for Arg-NMec (0.1 mM) and BANA (0.71 mM) all support the possibility that BANA-I is closely related to cathepsin H. In contrast, BANA-II is sensitive to Zn2+, leupeptin (Ki = 5.5 X 10(-9) M), is not adsorbed by concanavalin A- (Con-A)Sepharose, but is bound to organomercurial sepharose. It has a specificity to Z-Phe-Arg-NMec but not to Arg-NMec, has the molecular weight of 27, PI of 5.2, the pH optima for BANA (6.0), and the Km for BANA of 3.3 mM and the Km for Z-Phe-Arg-NMec of 0.1 mM. These features resemble those of liver cathepsin B. Leupeptin-sensitive BANA hydrolase was observed in the glandular extract of isolated sweat glands, which was increased after stimulation with methacholine and isoproterenol in vitro. The data are consistent with the notion that cathepsins B- and H-like enzymes are present in eccrine sweat and the former may be derived from the sweat gland.