Comparative study of the effect of 5' AMP and its analogs on rabbit glycogen phosphorylase b isoenzymes.

A comparative study of the effect of AMP and other nucleotides on the different rabbit glycogen phosphorylase b isoenzymes has been made: muscle, brain, liver isoenzymes, and the hybrid species between muscle and brain isoenzyme. We have studied either the direct kinetic effect of the different nucleotides or the action of the nucleotides on the b to a conversion rate. Muscle, brain, and muscle--brain isoenzymes are very strongly and very specifically activated by AMP and its analogs, whereas liver isoenzyme is not very sensitive to the nucleotides. However, muscle, brain and muscle--brain isoenzymes show slight but very interesting differences in their kinetic properties. These differences allow some speculations about the conformational state of these different isoenzymes.