Limited proteolysis by subtilisin reveals structural differences between phosphorylase a and b.
The limited proteolysis of rabbit skeletal muscle phosphorylase a and b was studied with subtilisin BPN' immoblized to Sepharose 4B. The activity of phosphorylase b is nearly resistant to subtilisin under the conditions (pH 7.0, 30 degrees C) where phosphorylase a rapidly loses its activity. The pH profile of phosphorylase a and b digestion is different. Proteolytic fragments of mol. wt 70,000 and 30,000 generated from phosphorylase a, while mol. wt 80,000 and 70,000 generated from phosphorylase b can be detected by SDS gel electrophoresis. Addition of AMP to phosphorylase b favours a conformation similar to--but not identical with--phosphorylase a as recognised by subtilisin action.
D000249:Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D006863:Hydrogen-Ion Concentration; D009132:Muscles / Q000201:enzymology; D010446:Peptide Fragments; D010762:Phosphorylase a / Q000378:metabolism*; D010763:Phosphorylase b / Q000378:metabolism*; D006005:Phosphorylases / Q000378:metabolism*; D011487:Protein Conformation; D011817:Rabbits; D013381:Subtilisins / Q000378:metabolism*
D010446:Peptide Fragments; D000249:Adenosine Monophosphate; D010762:Phosphorylase a; D010763:Phosphorylase b; D006005:Phosphorylases; D013381:Subtilisins