title: Human cathepsin H.
abstract: Cathepsin H was purified from human liver by a method involving autolysis and acetone fractionation, and chromatography on DEAE-cellulose, Ultrogel AcA 54, hydroxyapatite and concanavalin A-Sepharose. The procedure allowed for the simultaneous isolation of cathepsin B and cathepsin D. Cathepsin H was shown to consist of a single polypeptide chain of 28 000 mol.wt., and affinity for concanavalin A-Sepharose indicated that it was a glycoprotein. The enzyme existed in multiple isoelectric forms, the two major forms having pI values of 6.0 and 6.4; it hydrolysed azocasein (pH optimum 5.5), benzoylarginine 2-naphthylamide (Ba-Arg-NNap), leucyl 2-naphthylamide (Arg-NNap), (pH optimum 6.8). Arg-NNap and Arg-NMec, unlike Bz-Arg-NNap-, were not hydrolysed by human cathepsin B. Cathepsin H was similar to cathepsin B in being irreversibly inactivated by exposure to alkaline pH. Sensitivity to chemical inhibitors by 1 microM-leupeptin, which gave essentially complete inhibition of the other lysosomal cysteine proteinases, cathepsins B and L.
mesh_terms: D002403:Cathepsins / Q000037:antagonists & inhibitors / Q000302:isolation & purification*; D055598:Chemical Phenomena; D002621:Chemistry; D002848:Chromatography, DEAE-Cellulose; D002850:Chromatography, Gel; D006801:Humans; D007527:Isoenzymes / Q000302:isolation & purification; D008099:Liver / Q000201:enzymology*; D008722:Methods; D013379:Substrate Specificity; D000511:alpha-Macroglobulins / Q000494:pharmacology
chemical_list: D007527:Isoenzymes; D000511:alpha-Macroglobulins; D002403:Cathepsins