Ligand effects on the activity of the a form of various mammalian heart specific isophosphorylases.
1. The allosteric sensitivity of heart specific and skeletal muscle specific phosphorylase a-s from rabbit, pig, bovine and dog was compared. 2. 0.2-0.3 mM glucose 6-phosphate exerts 50% inhibition on the heart specific phosphorylase a-s without any inhibitory effect on the skeletal muscle specific ones. 3. AMP decreases the Km for substrates (glucose 1-phosphate, or Pi) of all heart specific phosphorylase a-s. It also enhances the Vmax of pig and bovine phosphorylase a-s 2-fold, but has no effect on the Vmax of rabbit and dog enzymes.
D000249:Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D004285:Dogs; D019298:Glucose-6-Phosphate; D005958:Glucosephosphates / Q000494:pharmacology; D007527:Isoenzymes / Q000037:antagonists & inhibitors; D008024:Ligands / Q000494:pharmacology*; D009132:Muscles / Q000201:enzymology; D009206:Myocardium / Q000201:enzymology*; D010762:Phosphorylase a / Q000037:antagonists & inhibitors*; D006005:Phosphorylases / Q000037:antagonists & inhibitors*; D011817:Rabbits; D013045:Species Specificity; D013237:Stereoisomerism; D013379:Substrate Specificity; D013552:Swine
D005958:Glucosephosphates; D007527:Isoenzymes; D008024:Ligands; D000249:Adenosine Monophosphate; D019298:Glucose-6-Phosphate; D010762:Phosphorylase a; D006005:Phosphorylases