Open AccessCrystallization and Properties of Cathepsin B from Rat Liver
Author(s) -
TOWATARI Takae,
KAWABATA Yoshimasa,
KATUNUMA Nobuhiko
Publication year - 1979
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1979.tb06290.x
Subject(s) - chemistry , biochemistry , isoelectric point , chromatography , sephadex , molecular mass , sodium dodecyl sulfate , isoelectric focusing , gel electrophoresis , polyacrylamide gel electrophoresis , arginine , enzyme , amino acid
Cathepsin B from rat liver was purified to apparent homogeneity by cell‐fractionation, freezing and thawing, acetone treatment, gel filtration, DEAE‐Sephadex and CM‐Sephadex column chromatography, and was crystallized. The purified enzyme formed spindle‐shaped crystals and its homogeneity was proved by disc gel electrophoresis in the presence of sodium dodecyl sulfate and by ultracentrifugical analysis. Its s 20,w value was 2.8 S and its relative molecular mass was calculated to be 22500 (± 900) by sedimentation equilibrium analysis. Crystalline cathepsin B was shown to consist of four isozymes with isoelectric points between pH 4.9 and 5.3, the main isozyme having an isoelectric point of pH 5.0. The enzyme was irreversibly inactivated by exposure to weak alkali. The pH optimum was 6.0 with α‐ N ‐benzoyl‐ dl ‐arginine‐4‐nitroanilide as substrate. Amino acid analysis showed that the enzyme contained hexosamine, glucosamine and galactosamine. Cathepsin B inactivated aldolase, glucokinase, apo‐ornithine aminotransferase, and apo‐cystathionase, but the rates of inactivation of glucokinase, apo‐ornithine aminotransferase, and apo‐cystathionase were lower than that of aldolase. Studies by polyacrylamide gel electrophoresis in the presence and absence of sodium dodecyl sulfate showed that cathepsin B degraded apo‐ornithine aminotransferase to two polypeptide chains differing in relative molecular mass and electrophoretic mobility.