Kinetic study on the dimer-tetramer interconversion of glycogen phosphorylase a.
Kinetic theory of dissociating enzyme systems has been applied to a study of the dimer-tetramer interconversion of glycogen phosphorylase a. All kinetic constants for the dissociating-associating reaction of phosphorylase a have been determined. The results indicate that (a) the presence of glucose-1-phosphate has no influence on either the rate of dissociation or the rate of association, and hence does not shift the dimer-tetramer equilibrium of phosphorylase a; (b) the binding og glycogen to the enzyme decreases the association rate of the dimer to form the tetramer, but has no effect on the dissociation rate of the tetramer; (c) both the dimeric and tetrameric form of phosphorylase a can bind glycogen, but the tetrameric form has a lower affinity for glycogen and is catalytically inactive.
Wang
Z X
ZX
National Laboratory of Biomacromolecules, Academia Sinica, Beijing, China. zxwang@sun5.ibp.ac.cn
D005958:Glucosephosphates / Q000494:pharmacology; D006003:Glycogen / Q000378:metabolism; D007700:Kinetics; D010762:Phosphorylase a / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation
D005958:Glucosephosphates; D006003:Glycogen; C031590:glucose-1-phosphate; D010762:Phosphorylase a