Separation and Some Characteristics of Two Factors from Rat Liver Particulate Fraction Which Stimulate and Inhibit the Low-Km Adenosine 3', 5' Cyclic Monophosphate (cAMP) Phosphodiesterase of Rat Fat Cells

Two factors were separated from rat liver particulate fraction treated with insulin, one of them having a stimulating effect on low-Km adenosine 3', 5' cyclic monophosphate (cAMP) phosphodiesterase activity of crude microsomal fraction (P-2 fraction) and the other having an inhibiting effect on the activity of low-Km cAMP phosphodiesterase solubilized with 0.3% Brij 58 from P-2 fraction. Trypsin and heat treatments had essentially no effect on these two factors.The stimulating factor did not significantly change the apparent Km value of enzyme in P-2 fraction but increased the maximal velocity of the reaction. The inhibiting factor raised the Km value of solubilized enzyme without affecting the maximal velocity of the reaction.The stimulating factor level in diabetic rat was larger than that in normal rat while the inhibiting factor level in diabetic rat was smaller than that in normal rat. possible participation of both factors in insulin action is discussed.