title: Proteasome and its novel endogeneous activator in human platelets.
abstract: Proteasome, a high molecular weight multicatalytic protease, was purified from the cytosolic fraction of human platelets for the first time. The biochemical properties of the enzyme including substrate specificity, optimal pH and effects of various inhibitors were almost identical with those of other cells. During the purification with a Heparin-Sepharose chromatography, a novel endogenous activator of the protease was identified and was partially purified. The activator enhanced both chymotrypsin or trypsin like activities of the proteasome in a dose related manner and was inactivated by heating at 56 degrees C for 30 min. This newly identified activator may serve as an important regulator or cofactor of intracellular activities of the proteasome.
authors.affiliation: Department of Surgery II, Osaka University Medical School, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Yukawa
authors.forename: M
authors.initials: M
authors.lastname: Sakon
authors.forename: J
authors.initials: J
authors.lastname: Kambayashi
authors.forename: E
authors.initials: E
authors.lastname: Shiba
authors.forename: T
authors.initials: T
authors.lastname: Kawasaki
authors.forename: H
authors.initials: H
authors.lastname: Ariyoshi
authors.forename: T
authors.initials: T
authors.lastname: Mori
mesh_terms: D000595:Amino Acid Sequence; D001792:Blood Platelets / Q000201:enzymology*; D002846:Chromatography, Affinity; D002852:Chromatography, Ion Exchange; D003546:Cysteine Endopeptidases / Q000097:blood* / Q000302:isolation & purification; D003600:Cytosol / Q000201:enzymology; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000097:blood* / Q000302:isolation & purification; D009842:Oligopeptides; D046988:Proteasome Endopeptidase Complex; D013379:Substrate Specificity
chemical_list: D009097:Multienzyme Complexes; D009842:Oligopeptides; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex