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Abstract

The ratio of the steady-state kinetic Hill coefficients of two different effectors equals (under some rather weak general assumptions) the ratio in which the effectors displace each other from an enzyme. This principle can make the implications of experimental allosteric enzyme kinetic data immediately transparent. One molecule of the allosteric inhibitor of dCMP aminohydrolase, at moderately high effector concentrations, displaces one molecule of substrate, or one molecule of activator, whereas at very high concentrations, one molecule of inhibitor displaces two of substrate. Further use of the principle suggests that substrate, at high concentrations, binds to activator sites. However ratios of substrate, activator and inhibitor Hill coefficients are incompatible with a simple model of activation in which substrate and activator are bound to the same conformation.

Additional information

Authors: WHITEHEAD E P, University of Roma (IT) and CEC, Bruxelles (BE);NUCCI R, CNR, Institute for Biochemistry of Proteins and Enzymology, Napoli (IT);RAIA C A, CNR, Institute for Biochemistry of Proteins and Enzymology, Napoli (IT);VACCARO C, CNR, Institute for Biochemistry of Proteins and Enzymology, Napoli (IT);ROSSI M, CNR, Institute for Biochemistry of Proteins and Enzymology, Napoli (IT)
Bibliographic Reference: Paper presented: 25 Years of Allostery, London (GB), Dec. 21, 1988
Availability: Available from (1) as Paper EN 34490 ORA
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