title: [Inhibition of muscle glycogen phosphorylase b by 5-methyltetrahydrofolic acid, 3'-chloro- and 3',6'-dichloromethotrexates].
abstract: Inhibition of rabbit skeletal muscle glycogen phosphorylase b by 5-methyl-5,6,7,8-tetrahydrofolic acid, 3'-chloro- and 3',5'-dichloromethotrexates has been studied. The inhibition is reversible and characterized by positive kinetic cooperativity (Hill coefficient exceeds 1). The values of pterin concentration causing two-fold diminishing of the enzymatic reaction rate increased in the order: 3',5'-dichloromethotrexate, 3'-chloromethotrexate, 5-methyl-5,6,7,8-tetrahydrofolic acid (0.24, 0.40 and 1.87 mM, respectively). Comparison of "half-saturation" concentrations for the above compounds and for methotrexate and folinic acid shows that pterin affinity to glycogen phosphorylase b is affected by substituents both in pteridine and in p-aminobenzoic moieties of the pterin molecule. The antagonism between 5-methyl-5,6,7,8-tetrahydrofolic acid, 3'-chloro- and 3',5'-dichloromethotrexates, on the one hand, and AMP and FMN, on the other, is revealed for combined action of modifiers on glycogen phosphorylase b.
authors.forename: S V
authors.initials: SV
authors.lastname: Klinov
authors.forename: B I
authors.initials: BI
authors.lastname: Kurganov
authors.forename: B M
authors.initials: BM
authors.lastname: Sheĭman
authors.forename: E Sh
authors.initials: ESh
authors.lastname: Gorelik
authors.forename: E M
authors.initials: EM
authors.lastname: Birinberg
mesh_terms: D000249:Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D005486:Flavin Mononucleotide / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D008727:Methotrexate / Q000031:analogs & derivatives* / Q000494:pharmacology; D009132:Muscles / Q000201:enzymology*; D010763:Phosphorylase b / Q000037:antagonists & inhibitors*; D006005:Phosphorylases / Q000037:antagonists & inhibitors*; D011817:Rabbits; D013763:Tetrahydrofolates / Q000494:pharmacology*
chemical_list: D013763:Tetrahydrofolates; D000249:Adenosine Monophosphate; C004763:3',5'-dichloromethotrexate; C058413:3'-chloromethotrexate; D005486:Flavin Mononucleotide; D010763:Phosphorylase b; D006005:Phosphorylases; C005984:5-methyltetrahydrofolate; D008727:Methotrexate
vernacular_title: Ongibirovanie myshechnoĭ glikogenfosforilazy b 5-metiltetragidrofolievoĭ kislotoĭ, 3'-khlor- i 3',5'-dikhlormetotreksatami.