Space-filling effects of inert solutes as probes for the detection and study of substrate-mediated conformational changes by enzyme kinetics: Theoretical considerations

Bergman D.A. and Winzor D.J. (1989) Space-filling effects of inert solutes as probes for the detection and study of substrate-mediated conformational changes by enzyme kinetics: Theoretical considerations. Journal of Theoretical Biology, 137 2: 171-189. doi:10.1016/S0022-5193(89)80204-8


Author Bergman D.A.
Winzor D.J.
Title Space-filling effects of inert solutes as probes for the detection and study of substrate-mediated conformational changes by enzyme kinetics: Theoretical considerations
Journal name Journal of Theoretical Biology   Check publisher's open access policy
ISSN 1095-8541
Publication date 1989-03-21
Sub-type Article (original research)
DOI 10.1016/S0022-5193(89)80204-8
Open Access Status Not yet assessed
Volume 137
Issue 2
Start page 171
End page 189
Total pages 19
Subject 1100 Agricultural and Biological Sciences
1300 Biochemistry, Genetics and Molecular Biology
2400 Immunology and Microbiology
2604 Applied Mathematics
2611 Modelling and Simulation
2613 Statistics and Probability
2700 Medicine
Abstract From expressions derived for the space-filling effects of small inert solutes on kinetic parameters for univalent enzymes undergoing isomerizations that are substrate-induced and pre-existing, it is concluded that experimental observation of an enhanced maximal velocity in the presence of inert solute can only reflect the existence of the former type of conformational change; and that the isomerization must be governed by a relatively small equilibrium constant. Similar conclusions apply to multivalent enzymes exhibiting Michaelis-Menten kinetics. Extension of the theory to provide quantitative expressions for multivalent enzymes has made possible the numerical simulation of thermodynamic non-ideality effects on systems conforming with the Monod and Koshland models of allostery. In that regard the simulated Scatchard plots for the two models differ sufficiently in form to suggest that detailed examination of the space-filling effects of small solutes on the kinetics of an allosteric enzyme may, under favourable circumstances, allow identification of the appropriate allosteric mechanism. Finally, these considerations of thermodynamic non-ideality in relation to the kinetics of allosteric enzymes have revealed formal similarities between the consequences of space-filling by inert solutes and the specific effects of allosteric activators or inhibitors. Attention is drawn to the possible implications of this observation in relation to the functioning of allosteric enzymes in vivo, where catalytic performance may be modified by factors no more specific than the ability of unrelated solutes to occupy space in the highly concentrated cellular environment.
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collection: Scopus Import - Archived
 
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