The activation of synthase (D to I conversion) has been shown to be slow in several tissues from fasted and diabetic animals. This may due to (a) lower or inhibited phosphoprotein phosphatase activity, (b) existance of modified (highly phosphorylated) forms of synthase which are poor substrates or, (c) both. Results of present investigation show that glycogen synthase from normal, epinephrine treated and diabetics rabbit skeletal muscle has 2.4, 3.85 and 3.91 moles of phosphate per mole subunit, respectively. The distribution of phosphate in the trypsin sensitive and trypsin insensitive phosphorylation regions in normal, epinephrine treated and diabetic rabbits was 0.95 and 1.4; 2.09 and 1.75 and 1.08 and 2.84, moles respectively, thus suggesting that cAMP-independent syntase kinase plays an important role in the phosphorylation of synthase in normal and diabetic rabbits. It is proposed to further investigate the in vivo phosphate content and distribution of phosphate in the trypsin sensitive and trypsin insensitive regions of synthase in skeletal muscle of fasted, insulin treated normal and insulin treated diabetic rabbits. The results of the study will be used to prepare purified 32P synthases with a phosphate content similar to that found in these rabbits. These 32P-synthase preparations will then be used to investigate the phosphoprotein phosphatase activities in normal, diabetic and insulin treated rabbits. In addition, the levels of phosphoprotein phosphatase inhibitor 1 and 2 will also be studies in these muscle extracts. The investigation will give further insight into the regulation of glycogen synthase and phosphoprotein phosphatase activity in rabbit skeletal muscle.
