title: Enzymatic properties of the proteasome purified from starfish oocytes and its catalytic subunits involved in oocyte maturation.
abstract: The 20S proteasome was purified from oocytes of the starfish Asterina pectinifera and its enzymatic properties were investigated. The chymotrypsin-like activities were potently inhibited by PSI as well as MG115, whereas the trypsin-like and peptidyl-glutamyl peptide-hydrolyzing (PGPH) activities were not or only weakly inhibited by PSI and MG115. The inhibitory ability of MG115 toward germinal vesicle breakdown (GVBD) coincided with those toward the trypsin-like and PGPH activities, and PSI showed no inhibitory effect on GVBD. We have previously reported that the inhibition pattern toward GVBD of peptidyl-argininals, which potently inhibited the proteasomal trypsin-like activity rather than the chymotrypsin-like activity, correlated with the inhibition pattern toward the chymotrypsin-like activity of the proteasome. These results, together with the peptidyl-argininals scarcely inhibiting the PGPH activity at concentrations sufficient for the inhibition toward GVBD, indicate that both the chymotrypsin-like and trypsin-like activities, but not the PGPH activity, of the proteasome are responsible for degradation of the physiological substrate during starfish oocyte maturation. It was also suggested that the inhibition of a single catalytic site of the proteasome is not sufficient for prevention of the proteasomal function.
authors.affiliation: Department of Biochemistry, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812 , Japan.
authors.forename: E
authors.initials: E
authors.lastname: Tanaka
authors.forename: M
authors.initials: M
authors.lastname: Takagi Sawada
authors.forename: H
authors.initials: H
authors.lastname: Sawada
mesh_terms: D000818:Animals; D002384:Catalysis; D002453:Cell Cycle; D002454:Cell Differentiation / Q000502:physiology*; D002918:Chymotrypsin / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000302:isolation & purification / Q000494:pharmacology*; D005260:Female; D009097:Multienzyme Complexes / Q000302:isolation & purification / Q000494:pharmacology*; D009865:Oocytes / Q000737:chemistry* / Q000254:growth & development*; D046988:Proteasome Endopeptidase Complex; D013215:Starfish / Q000502:physiology*; D014357:Trypsin / Q000378:metabolism
chemical_list: D009097:Multienzyme Complexes; D002918:Chymotrypsin; D014357:Trypsin; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex