ENZYMORPHOLOGIC DEMONSTRATION OF GLUCOSE 6-PHOSPHATE-DEPENDENT GLYCOGEN SYNTHETASE IN MOUSE LIVER

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Abstract
Mouse liver possesses G-6-P-dependent glycogen synthetase and not the G-6-P-independent variety. This fact explains the higher requirement (450mg per 25 ml) for G-6-P in the incubation mixture for staining mouse liver glycogen synthetase than that present in the Takeuchi and Glenner substrate mixture. The higher G-6-P content, as well as other considerations, necessitated the establishment of new conditions for the staining reaction for glycogen synthetase, i.e., pH 9.4, UDPG concentration 200 mg per 25 ml, etc. The presensce of NaF (4.8 x 10–2 M) prevents thermal inactivation of glycogen synthetase at 37°, which is the temperature now recommended for the staining reaction. Postfixation and dehydration makes the sections more readily interpretable and prolongs markedly the life of the iodine staining reaction. The new procedure is reproducible and consistent in serial sections of the same animal and among different animals of like glycogen content. The enzyme appears to be located on membranes as well as in granules. Some similarities between the characteristics of the dependent and independent forms of the enzyme, as we and others have observed them by both histochemical and biochemical techniques, are discussed.