San Juan Serrano F, Fernández González M, Sánchez López JL, García Martín LO. Modification of kinetic parameters of glycogen phosphorylase from mantle tissue of Mytilus galloprovincialis by a phosphorylation mechanism.
Int J Biochem Cell Biol 1995;
27:917-22. [PMID:
7584627 DOI:
10.1016/1357-2725(95)00059-x]
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Abstract
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.
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