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Higher Glucose Affinity of Hexokinase in Sheep Brain than in Rat Brain


THE brain in sheep, as in non-ruminant mammals' appears dependent on glucose as the substrate for oxidation1, yet the blood glucose concentration of adult sheep is only about 2.5 mM (50 mg/100 ml.) compared with about 5 mM (100 mg/100 ml.) in rats, dogs, men and pigs. If the availability of a substrate is less in one species than in another, and a tissue were to utilize the substrate at comparable rates in both species, then one might look for an inter-species difference in enzyme affinity for this substrate. So we have estimated the apparent Km for glucose of hexokinase in brain, also liver, muscle and adiposa, of sheep and rats.

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RAGGI, F., KRONFELD, D. Higher Glucose Affinity of Hexokinase in Sheep Brain than in Rat Brain. Nature 209, 1353–1354 (1966).

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