Catalytic site of glycogen phosphorylase: structure of the T state and specificity for .alpha.-D-glucose

alpha -D-Glucose inhibits glycogen phosphorlase a by binding at the catalytic site of the inactive conformer (T state) at the same position as does the substrate alpha -D-glucose 1-phosphate to the active (R state) enzyme. It is established that recognition of glucose 1-phosphate is highly specific. Here the authors show by crystallographic analysis of the alpha -D-glucose-phosphorylase a complex and by analysis of inhibition by a variety of glucose analogues the nature and specificity of the recognition of the glucosyl group by the T-state enzyme.