Modification of kinetic parameters of glycogen phosphorylase from mantle tissue of Mytilus galloprovincialis by a phosphorylation mechanism

• Published in: The international journal of biochemistry & cell biology Vol. 27; no. 9; pp. 917 - 922
• Main Authors: Serrano, Fuencisla San Juan, González, Margarita Fernández, López, JoséLuis Sánchez, Martín, L.Oscar Garcia
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Ltd 01.09.1995
• Subjects: Adenosine Monophosphate - pharmacology; Animals; Bivalvia - enzymology; Glycogen - metabolism; Kinetic parameters; Kinetics; Mytilus; Phosphates - metabolism; Phosphorylase; Phosphorylase a - metabolism; Phosphorylase b - metabolism; Phosphorylases - metabolism; Phosphorylation; Substrate Specificity; Kinetic parameters; Phosphorylase; Mytilus
• ISSN: 1357-2725; 1878-5875
• DOI: 10.1016/1357-2725(95)00059-X

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 ( K m) are 0.05 mg/ml glycogen, 1.15 mM inorganic phosphate and 1.50 mM glucose-1-phosphate. The K ms 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.