A ‘top-down’ approach to the determination of control coefficients in metabolic control theory

Authors


Correspondence to R. P. Hafner, Department of Biochemistry, Tennis Court Road. Cambridge CB2 1QW, England

Abstract

A new approach to the determination of flux and concentration control coefficients in metabolic pathways is outlined. Linear pathways are conceptually divided in two around an intermediate metabolite (or group of metabolites) and the control coefficients of the two parts are derived from the elasticity coefficients of the two parts to the intermediate. Branched pathways are treated similarly, the control coefficients of the branches being derived either from the elasticities of the branches to their common intermediate or from the relative flux changes of the branches. Repeating this analysis around other intermediates in the pathway allows the control coefficients of smaller and smaller groups of enzymes to be determined. In complex systems this approach to describing control may have several advantages over determining the control coefficients of individual enzymes and is a potentially useful complementary approach.

Symbols
EA

enzyme(s) A (enzyme or transporter)

JA

steady state flux through EA

ɛAX

elasticity of flux through EA with respect to substance X

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control coefficient of EA on the flux (or substance) J

δAB

partial derivative of A with respect to B

δA

(small) change in A

X

concentration of substance X

Ancillary