Regulation of the dephosphorylation of phosphorylase A by glucose, AMP and polyamines.
1. The effect of glucose, caffeine, AMP and polyamines was investigated on the dephosphorylation of phosphorylase a by the catalytic subunits of protein phosphatase-1 and -2A. 2. Caffeine at 1-20 microM inhibited the dephosphorylation of the dimeric phosphorylase a at 37 degrees C using skeletal muscle enzymes; 0.1-10 mM of caffeine enhanced the rate of dephosphorylation greatly at 13 degrees C and slightly at 37 degrees C. 3. alpha-D-Glucose was more effective in accelerating both the dephosphorylation and the tryptic digestion of phosphorylase a than the beta-anomer. 4. Polyamines were found to moderate the inhibitory effect of AMP at concentrations which may occur in the tissues. In the presence of 5 mM glucose polyamines could cancel the AMP inhibition of the dephosphorylation of liver phosphorylase a by hepatic protein phosphatase-1 and -2A.
Farkas
I
I
Institute of Medical Chemistry, University School of Medicine, Debrecen, Hungary.
Tóth
B
B
Gergely
P
P
D000249:Adenosine Monophosphate / Q000494:pharmacology*; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D005947:Glucose / Q000494:pharmacology*; D008099:Liver / Q000201:enzymology; D009132:Muscles / Q000201:enzymology; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010762:Phosphorylase a / Q000378:metabolism*; D006005:Phosphorylases / Q000378:metabolism*; D010766:Phosphorylation; D011073:Polyamines / Q000494:pharmacology*; D054645:Protein Phosphatase 1; D011700:Putrescine / Q000494:pharmacology; D011817:Rabbits; D013095:Spermidine / Q000494:pharmacology; D013096:Spermine / Q000494:pharmacology; D013696:Temperature
D011073:Polyamines; D013096:Spermine; D002110:Caffeine; D000249:Adenosine Monophosphate; D010762:Phosphorylase a; D006005:Phosphorylases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D005947:Glucose; D013095:Spermidine; D011700:Putrescine