0100488810

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STUDIES ON GLYCOGEN PHOSPHORYLASE KINASE : CATALYTIC PROPERTIES AND ISOZYMES

English (英語)

The Kobe journal of the medical sciences

28(2)

75-90

1982-04

The present study is concerned with the multiple functions and isozymes of glycogen phosphorylase kinase. Skeletal muscle glycogen phosphorylase kinase [EC 2.7.1.38] is able to phosphorylate in vitro multiple species of unidentified proteins from various subcellular fractions of rat liver. The phosphorylation is dependent on the presence of ca2+. Phosphate acceptor proteins of subcellular fractions are most abundant in the soluble and microsomal fractions. The spectrum of phosphate acceptor proteins entirely differs from that for cyclic AMP-dependent protein kinase (protein kinase A). The enzyme also phosphorylates calf thymus histone fractions and Hl histone is the most preferable substrate. The phosphorylation sites in Hl histone for this enzyme are different from those for protein kinase A by N-bromosuccinimide bisection and fingerprint analysis. It is suggested that the enzyme is potentially multifunctional and plays roles in controlling some of the Ca2+ dependent processes. Properties of glycogen phosphorylase kinase, present in 100,000 x g supernatant from various rat tissues, were examined. The enzymes appear to be divided into at least three types; muscle, brain and liver types. The muscle and liver types are distinguished from each other in the pH 6.8/8.5 activity ratio, Ca2+ dependency, activation by protein kinase A and inhibition by the antiserum. The enzymes from heart and skeletal muscle belong to the muscle type, and those from liver, kidney, spleen, lung and testis to the liver type. The enzyme from brain apparently differs from these types and seems to be an intermediate type or mixture of the two.

antiserum

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