title: Glucose-6-phosphate isomerase is an endogenous inhibitor to myofibril-bound serine proteinase of crucian carp (Carassius auratus).
abstract: Glucose-6-phosphate isomerase (GPI) was purified to homogeneity from the skeletal muscle of crucian carp ( Carassius auratus ) by ammonium sulfate fractionation, column chromatographies of Q-Sepharose, SP-Sepharose, and Superdex 200 with a yield of 8.0%, and purification folds of 468. The molecular mass of GPI was 120 kDa as estimated by gel filtration, while on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), two subunits (55 and 65 kDa) were identified, suggesting that it is a heterodimer. Interestingly, GPI revealed specific inhibitory activity toward a myofibril-bound serine proteinase (MBSP) from crucian carp, while no inhibitory activity was identified toward other serine proteinases, such as white croaker MBSP and crucian carp trypsin. Kinetic analysis showed that GPI is a competitive inhibitor toward MBSP, and the K(i) was 0.32 microM. Our present results indicated that the multifunctional protein GPI is an endogenous inhibitor to MBSP and may play a significant role in the regulation of muscular protein metabolism in vivo.
authors.affiliation: College of Biological Engineering, The Key Laboratory of Science and Technology for Aquaculture and Food Safety, Jimei University, Jimei, Xiamen, China.
authors.forename: Le-Chang
authors.initials: LC
authors.lastname: Sun
authors.forename: Li-Gen
authors.initials: LG
authors.lastname: Zhou
authors.forename: Cui-Hong
authors.initials: CH
authors.lastname: Du
authors.forename: Qiu-Feng
authors.initials: QF
authors.lastname: Cai
authors.forename: Kenji
authors.initials: K
authors.lastname: Hara
authors.forename: Wen-Jin
authors.initials: WJ
authors.lastname: Su
authors.forename: Min-Jie
authors.initials: MJ
authors.lastname: Cao
mesh_terms: D000818:Animals; D002347:Carps / Q000378:metabolism*; D029941:Fish Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D005956:Glucose-6-Phosphate Isomerase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008970:Molecular Weight; D018482:Muscle, Skeletal / Q000737:chemistry / Q000201:enzymology; D009210:Myofibrils / Q000737:chemistry / Q000201:enzymology*; D011485:Protein Binding; D012697:Serine Endopeptidases / Q000737:chemistry / Q000378:metabolism*; D015842:Serine Proteinase Inhibitors
chemical_list: D029941:Fish Proteins; D015842:Serine Proteinase Inhibitors; D012697:Serine Endopeptidases; D005956:Glucose-6-Phosphate Isomerase