Butler PE, Cookson EJ, Beynon RJ. The turnover of skeletal muscle glycogen phosphorylase studied using the cofactor, pyridoxal phosphate, as a specific label.
BIOCHIMICA ET BIOPHYSICA ACTA 1985;
847:316-23. [PMID:
4063401 DOI:
10.1016/0167-4889(85)90037-0]
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Abstract
The turnover of glycogen phosphorylase has been measured using the cofactor, pyridoxal phosphate, as a label specific for this enzyme in skeletal muscle. Radiolabelled pyridoxine administered in vivo is incorporated into a protein-bound fraction in skeletal muscle, shown by several criteria to be equivalent to glycogen phosphorylase. This pool of radiolabel disappears slowly with a half-life of 11.9 days, taken to be a good estimate of the intracellular half-life of the enzyme. The use of the cofactor in this fashion minimises overestimation of half-life that results from reincorporation of the label. Further, premature dissociation of the cofactor from native enzyme, which would lead to underestimation of half-life, is unlikely. At the level of sensitivity given by this method there was little evidence for the appearance of pyridoxal phosphate-labelled degradation intermediates of the enzyme.
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