Journal article
Effects of 1,2-dimethoxyethane on the catalytic and coenzyme properties of glycogen phosphorylase
Biochemistry (Easton), Vol.20(9), pp.2537-2544
04/01/1981
DOI: 10.1021/bi00512a027
PMID: 6786337
Abstract
Dimethoxyethane, a good activator of phosphorylase b, has been used to study mechanisms of phosphorylase activation and the catalytic reaction. Activation can be explained best by an alteration of the allosteric equilibrium in favor of the active R conformation. Lesser effects are seen with phosphorylase a, and activation does not alter appreciably the equilibrium between the dimeric and tetrameric forms. With 20% 1,2-dimethoxyethane, the Vm value of phosphorylase b is 74% of that obtained in the presence of adenosine monophosphate. In the presence of 10% 1,2-dimethoxyethane, the Ki value for glucose inhibition is increased 3-fold, but inhibition by 1,5-gluconolactone is increased. The allosteric activation of glycogen phosphorylase results in a change in pK1 for the pH-activity profile. The formation of the dianionic form of the phosphoryl group of the coenzyme, pyridoxal phosphate, may account for this change. By analogy to the effects of anions and a change in dielectric on the acid hydroylsis of glucose 1-phosphate, it is suggested that the dianion of the coenzyme could stabilize the developing positive charge of an oxonium ion intermediate. Dimethoxyethane also affects the interaction of pyridoxal phosphate with phosphorylase. It influences the rates of both resolution and reconstitution. Good preparations of apophosphorylase a can be made by using 1,2-dimethoxyethane in the resolution medium.
Details
- Title: Subtitle
- Effects of 1,2-dimethoxyethane on the catalytic and coenzyme properties of glycogen phosphorylase
- Creators
- Ronald J UhingSteven R LentzDonald J Graves
- Resource Type
- Journal article
- Publication Details
- Biochemistry (Easton), Vol.20(9), pp.2537-2544
- Publisher
- American Chemical Society
- DOI
- 10.1021/bi00512a027
- PMID
- 6786337
- ISSN
- 0006-2960
- eISSN
- 1520-4995
- Language
- English
- Date published
- 04/01/1981
- Academic Unit
- Hematology, Oncology, and Blood & Marrow Transplantation; Internal Medicine
- Record Identifier
- 9984094768902771
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