title: [Covalent modification of glycogen synthase I in rabbit skeletal muscle by 5'-fluorosulfonylbenzoyl derivatives of uridine].
abstract: Preincubation of rabbit skeletal muscle glycogen synthase I with 5'(p-fluorosulfonylbenzoyl)uridine (p-FSBU) or 5'-(m-fluorosulfonylbenzoyl)uridine (m-FSBU) results in a decrease of the enzymatic activity with time. UDP, the product of the glycogen synthase reaction, protects the enzyme against inactivation. It was shown that the covalent binding of the enzyme with each of its inhibitors is preceded by the formation of a reversible complex with Ki = 0.285 and 1.820 mM for p-FSBU and m-FSBU, respectively. This reaction is of pseudo-first order with respect to the inhibitors. The K2 values for p-FSBU and m-FSBU are nearly identical, i. e. 0.050 and 0.042 min-1, respectively, which suggests modification of the same functional group of the enzyme. The number and reactivity of the SH-groups of glycogen synthase I were determined, using 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB). The total number of SH-groups determined in the presence of 8 M urea is six as calculated per enzyme monomer. In the native enzyme DTNB titrates two SH-groups which according to their reactivity can be subdivided into 2 groups. The more reactive SH-group is localized in the active center of the enzyme. p-FSBU induces covalent blocking or screening of this SH-group during specific interaction with the active site of glycogen synthase I.
mesh_terms: D000818:Animals; D004228:Dithionitrobenzoic Acid / Q000378:metabolism; D006006:Glycogen Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D066298:In Vitro Techniques; D007700:Kinetics; D009132:Muscles / Q000201:enzymology*; D011817:Rabbits; D013438:Sulfhydryl Compounds / Q000378:metabolism; D014529:Uridine / Q000031:analogs & derivatives* / Q000494:pharmacology; D014530:Uridine Diphosphate / Q000378:metabolism
chemical_list: C040909:5'-(3-fluorosulfonylbenzoyl)uridine; C040910:5'-(4-fluorosulfonylbenzoyl)uridine; D013438:Sulfhydryl Compounds; D014530:Uridine Diphosphate; D004228:Dithionitrobenzoic Acid; D006006:Glycogen Synthase; D014529:Uridine
vernacular_title: Kovalentnaia modifikatsiia glikogensintazy I skeletnykh myshts krolika 5'-ftorsul'fonilbenzoil'nymi proizvodnymi uridina.