Canadian Medical Guide > Biological Sciences > Biochemical Phenomena, Metabolism, and Nutrition > Metabolism > Energy Metabolism > Substrate Cycling Terms and Definitions

Substrate Cycling

Medical Definition:	A set of opposing, nonequilibrium reactions catalyzed by different enzymes which act simultaneously, with at least one of the reactions driven by ATP hydrolysis. The results of the cycle are that ATP energy is depleted, heat is produced and no net substrate-to-product conversion is achieved. Examples of substrate cycling are cycling of gluconeogenesis and glycolysis pathways and cycling of the triglycerides and fatty acid pathways. Rates of substrate cycling may be increased many-fold in association with hypermetabolic states resulting from severe burns, cold exposure, hyperthyroidism, or acute exercise.
Guide Notes:	restricted to enzyme activity; almost never IM; coord NIM with specific enzyme (IM)
Also Called:	Futile Cycles
Previously Indexed:	Energy Metabolism (1975-1988),specific substance/metabolism (1975-1988)

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