Histones histone phosphorylases

Recent studies have shown that cyclic AMP-dependent protein kinases are present in many cells, and that these may phosphorylate protamine, histone, casein, phosphorylase kinase, and presumably other proteins as well. Kuo and Greengard (21) have proposed that cyclic AMP mediates all of its actions by activating specific protein kinases in various tissues. The tissue-specific effects of cyclic AMP on a given tissue would then be accounted for in terms of the specific protein kinase and its substrates in that tissue. The apparent Michaelis constants for activation by cyclic AMP are from 2 X 10 Af to 3 X 10 M, and it has been suggested that the... 

Histone H2A, H2B, H3, H4 Phosphoglycerate kinase Glycogen phosphorylase NAD glycohydrolase, Acteylchohne rezeptor... 

The formulas show the a-carbon and the side chain of the amino acid residues, line phosphatase, phosphorylase kinase, glycogen synthetase, troponin, RNA polymerase, polynucleotide, phosphorylase, and triglyceride lipase. Phosphoserine is also found in nonenzyme proteins which include histones, protamiens, ribosomal proteins, membrane proteins, ovalbumin, casein, and phosvitin often in substantial amounts. For example, there are 119 phosphoserines and only one phosphothreonine residue in phosvitin (72). 

Some of the regulatory enzymes involved in the phosphorylation/dephosphorylation of helminth glycolytic enzymes have been characterized. Two distinct protein kinases have been purified from A. suum muscle (25,26). One is cAMP-dependent and appears to be similar to the corresponding mammalian enzyme. Its apparent for PFK is similar to the intracellular concentration of the PFK, suggesting that PFK may be a substrate in vivo. The second kinase activity is cAMP-independent and not affected by the A. suum cAMP binding protein, Walsh inhibitor, ox heart R subunit or antiserum to the ox heart cAMP-dependent protein kinase (25). This kinase phosphorylates histone, phosvitin, and the A. suum PFK and phosphorylase b. It is responsible for about 75% of the PFK phosphorylating ability in A. suum muscle homogenates. 

Three protein phosphatase activities have been isolated from rabbit skeletal muscle protein phosphatase I (mol. wt. 3 x 10 , an active histone phosphatase) exhibited only little glycogen synthase phosphatase-1 and -2, phosphorylase... 

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