Biosynthesis of bacterial glycogen. The nature of the binding of substrates and effectors to ADP-glucose synthase

Thomas H Haugen; Jack Preiss

doi:10.1016/S0021-9258(17)30281-8

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Biosynthesis of bacterial glycogen. The nature of the binding of substrates and effectors to ADP-glucose synthase

Journal article

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Biosynthesis of bacterial glycogen. The nature of the binding of substrates and effectors to ADP-glucose synthase

Thomas H Haugen and Jack Preiss

The Journal of biological chemistry, Vol.254(1), pp.127-136

01/10/1979

DOI: 10.1016/S0021-9258(17)30281-8

PMID: 363717

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Abstract

Kinetic studies with ADP-glucose synthase show that 1,6-hexanediol bisphosphate (1,6-hexanediol-P2) is an effective activator that causes the enzyme to have a higher apparent affinity for ATP- and ADP-glucose than when fructose-1,6-P2 is the activator. Furthermore, in the presence of 1,6-hexanediol-P2, substrate saturation curves are hyperbolic shaped rather than sigmoidal shaped. CrATP behaves like a nonreactive analogue of ATP. Kinetic studies show that it is competitive with ATP. CrATP is not a competitive inhibitor of ADP-glucose. However, the combined addition of CrATP and glucose-1-P inhibits the enzyme competitively when ADP-glucose is the substrate. In binding experiments, CrATP, ATP, and fructose-P2 appear to bind to only half of the expected sites in the tetrameric enzyme, while ADP-glucose, the activators, pyridoxal-P and 1,6-hexanediol-P2, and the inhibitor, AMP, bind to four sites/tetrameric enzyme. Fructose-P2 inhibits 1,6-hexanediol-P2 binding, suggesting competition for the same sites. Glucose-1-P does not bind to the enzyme unless MgCl2 and CrATP are present and binds to four sites/tetrameric enzyme. Alternatively, CrATP in the presence of glucose-1-P binds to four sites/tetrameric enzyme. Thus, there are binding sites for the substrates, activators, and inhibitor located on each subunit and the binding sites can interact homotropically and heterotropically. ATP and fructose-P2 binding is synergistic showing heterotropic cooperativity. ATP and fructose-P2 must also be present together to effectively inhibit AMP binding. A mechanism is proposed which explains some of the kinetic and binding properties in terms of an asymmetry in the distribution of the conformational states of the four identical subunits.

Escherichia coli - enzymology

Glycogen - biosynthesis

Organophosphorus Compounds

Protein Binding

Substrate Specificity

Glycols

Enzyme Activation

Kinetics

Nucleotidyltransferases - metabolism

Adenosine Diphosphate Glucose

Details

Title: Subtitle: Biosynthesis of bacterial glycogen. The nature of the binding of substrates and effectors to ADP-glucose synthase
Creators: Thomas H Haugen
Jack Preiss
Resource Type: Journal article
Publication Details: The Journal of biological chemistry, Vol.254(1), pp.127-136
DOI: 10.1016/S0021-9258(17)30281-8
PMID: 363717
NLM abbreviation: J Biol Chem
ISSN: 0021-9258
eISSN: 1083-351X
Publisher: United States
Language: English
Date published: 01/10/1979
Academic Unit: Pathology
Record Identifier: 9984047616402771

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