Complementation of Subunits from Glycogen Phosphorylases of Frog and Rabbit Skeletal Muscle and Rabbit Liver

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Abstract
Activity can be induced in potentially active rabbit skeletal muscle phosphorylase monomers covalently bound to Sepharose by noncovalent interaction with soluble subunits carrying inactive pyridoxal 5''-phosphate analogs or even salicylaldehyde. These analogs are themselves incapable of reconstituting active holophosphorylase from apophosphorylase. Phosphorylases with 1 intrinsically inactive and 1 potentially active subunit have .apprx. 1/2 of the activity of the native phosphorylase dimer. The usefulness of this technique for subunit complementation was demonstrated by forming hybrid phosphorylases with inactive Sepharose-bound rabbit skeletal muscle subunits containing pyridoxal 5''-phosphate monomethylester and soluble activatable frog muscle and rabbit liver phosphorylase monomers. The inactive Sepharose-bound subunit induced in each case activity in the soluble subunit. The inactive rabbit muscle phosphorylase subunit transmitted its characteristic temperature dependence of the rate of the reaction to the frog muscle subunit; but it could not propagate its control properties to the liver enzyme. Differences of hybrid phosphorylases are related to immunological and amino acid divergencies among the component enzymes.