Stabilization of glucose-6-phosphatase activity by a 21 000-dalton hepatic microsomal protein

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Abstract
Hepatic microsomal glucose-6-phosphatase activity was rendered extremely unstable by a variety of techniques: (a) incubation at pH 5.0; (b) extraction of the microsomal fraction in the presence of 1% Lubrol; (c) various purification procedures. 2. These techniques all result in the removal of a 21 kDa polypeptide from the fraction containing glucose-6-phosphatase activity. 3. The 21 kDa protein was purified to apparent homogeneity by solubilization in the detergent Lubrol 12A-9 and chromatography on Fractogel TSK DEAE-650(S) and centrifugation at 105000 g. 4. The 21 kDa protein stabilizes glucose-6-phosphatase activity, whereas other purified hepatic microsomal proteins do not. 5. The 21 kDa protein appears to be a potential regulator of glucose-6-phosphatase activity.