Insulin-induced increases in the activity of the spontaneously active and ATP.Mg-dependent forms of phosphatase-1 in alloxan-diabetic rat liver.
Liver supernatant from normal and alloxan-diabetic rats was fractionated by DEAE-cellulose chromatography and the separated phosphoprotein phosphatase fractions were assayed with [32P]histone f2b, [32P]phosphorylase a and [32P]phosphorylase kinase as substrates. In diabetic rat liver, one of the phosphatase fractions found in the normal liver was significantly reduced. This fraction was identified as a mixture of the spontaneously active form and the ATP . Mg-dependent form of phosphoprotein phosphatase-1 (Fc) based on sensitivity to inhibitor-2, substrate specificity, and the fact that it could be activated 42-70% by glycogen synthase kinase-3 in the presence of ATP . Mg. Further analysis of this fraction showed that liver cytosol from diabetic rats contained 62-79% lower spontaneously active phosphatase-1 activity and 40-51% lower combined spontaneously active and ATP . Mg-dependent protein phosphatase-1 (Fc) activity. Insulin administration increased the spontaneously active and the ATP . Mg-dependent protein phosphatase-1 activities approximately 45% and 36%, respectively, in alloxan-diabetic rats. These data imply that the lower levels of spontaneously active phosphatase-1 activity in diabetic rat liver cannot be explained by presuming phosphatase-1 to have been present as Fc, the inactive form. Moreover, insulin restored the total activity of the spontaneously active and activatable forms of phosphatase-1 to those present in normal liver implying that both forms of phosphatase-1 activity are under hormonal control.
Dragland-Meserve
C J
CJ
Webster
D K
DK
Parker Botelho
L H
LH
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002848:Chromatography, DEAE-Cellulose; D003921:Diabetes Mellitus, Experimental / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects; D007328:Insulin / Q000494:pharmacology*; D008099:Liver / Q000201:enzymology*; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D054645:Protein Phosphatase 1; D051381:Rats; D011919:Rats, Inbred Strains
D007328:Insulin; D000255:Adenosine Triphosphate; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D008274:Magnesium