The Effect of Insulin on Individual Enzyme Systems

Insulin did not react as an accelerator but exerted its effects only under the conditions specified above. The Coris proposed that in diabetic tissue the inhibitory reactions of adrenocortical extracts depend on the presence of a substance of pituitary origin. Highly purified extracts of adrenotropic, lactogenic, and growth hormones were ineffective as inhibitors in conjunction with adrenocortical extracts. The Coris inhibitory substance had unusual lability, since (1) the initial inhibition effect on the hexokinase reaction is relieved by time, and (2) complete destruction of the inhibitory factor is observed by aging of extract for 45 to 120 minutes at 0°C. 

These results have been challenged by Mirsky and Stadie and their co-workers, who have not confirmed these observations. However, the recent work of Chaikoff and the experiments of Weil-Malherbe, who finds that the plasma of untreated diabetic patients inhibits brain hexokinase and that the degree of inhibition is correlated with the severity of the disease, strongly support the original contentions of the Cori group. 

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The Effect of Insulin on Individual Enzyme Systems. The pioneering work in this field of approach has been carried out by the Coris and their co-workers. They observed that in muscle extracts of alloxan-diabetic rats, of thirty animals, fifteen exhibited hexokinase activity which was inhibited 21% to 76% by the addition of an adrenal cortex extract, whereas the remaining fifteen showed less than 15% inhibition. This inhibition could not be observed with extracts of normal rat muscles. Brain and muscle hexokinase were inhibited by the addition of certain... 

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