Specificity of glucose 1,6-bisphosphate synthesis in rabbit skeletal muscle

1. To compare glucose 1,6-bisphosphate synthesis in different types of cells, we partially purified (2000-fold) a glycerate 1,3 P2-dependent glucose 1,6-bisphosphate synthase from rabbit skeletal muscle. 2. In agreement with the results reported by others for mouse brain and pig skeletal muscle, the enzyme can be separated from bulk phosphoglucomutase (PGM) activity by DEAE-cellulose chromatography of crude cellular extract. This cannot be achieved on human hemolysates where glycerate 1,3-P2-dependent glucose 1,2-bisphosphate synthesis is displayed only by multifunctional PGM2 isoenzymes. 3. The Km values for glycerate 1,3-P2 (0.50 microM), glucose 1-phosphate (90 microM), Mg2+ (0.22 mM), and also pH optimum (7.8) and mol. wt (70,000) of the rabbit skeletal muscle enzyme are similar to those of the enzymes from mouse brain and human red blood cells, but they differ from those reported for the pig skeletal muscle enzyme.