Modification of kinetic parameters of glycogen phosphorylase from mantle tissue of Mytilus galloprovincialis by a phosphorylation mechanism.
Initial rate and affinity studies on mantle Mytilus phosphorylase a were carried out in order to find possible differences in its kinetic properties with respect to phosphorylase b. Phosphorylase a was not stimulated for any AMP concentrations. Michaelis constants (Km) are 0.05 mg/ml glycogen, 1.15 mM inorganic phosphate and 1.50 mM glucose-1-phosphate. The Kms for the substrates, in the direction of glycogen breakdown, are enhanced by non-saturating concentrations of cosubstrate, without reducing the apparent maximum velocity. First order and hyperbolic kinetics and values of the allosteric constant smaller than 2 were observed. These results suggest a catalytic mechanism different to that shown for mantle Mytilus phosphorylase b.
San Juan Serrano
F
F
Departamento de Bioquímica y Biología Molecular, Facultad de Farmacia, Universidad de Santiago de Compostela, Spain.
Fernández González
M
M
Sánchez López
J L
JL
García Martín
L O
LO
D000249:Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D049872:Bivalvia / Q000201:enzymology*; D006003:Glycogen / Q000378:metabolism; D007700:Kinetics; D010710:Phosphates / Q000378:metabolism; D010762:Phosphorylase a / Q000378:metabolism*; D010763:Phosphorylase b / Q000378:metabolism*; D006005:Phosphorylases / Q000378:metabolism*; D010766:Phosphorylation; D013379:Substrate Specificity
D010710:Phosphates; D000249:Adenosine Monophosphate; D006003:Glycogen; D010762:Phosphorylase a; D010763:Phosphorylase b; D006005:Phosphorylases