PHYSIOLOGICAL SIGNIFICANCE OF POSITIVE AND NEGATIVE COOPERATIVITY IN ENZYMES

Glyceraldehyde-3-phosphate dehydrogenases from mammalian muscle and yeast are known to display negative and positive cooperativity, respectively, in the binding of coenzyme, NAD. A possible physiological role of these coenzyme-binding anomalies is raised by comparing them to the coenzyme-binding properties of lactate dehydrogenase and alcohol dehydrogenase, the corresponding glycolytic NADH-reoxidizing enzymes in muscle and yeast. It is suggested that the observed coenzyme-binding relations reflect the evolutionary adaptation of enzymes to facilitate vectorial metabolite flow. © 1979.