Studies involving enzymic phosphorylation. 1. The hexokinase activity of rat tissues

Abstract

Homogenates of several rat tissues were assayed for hexokinase activity using the rate of glucose disappearance in the presence of adenosinetriphosphate as a measure of activity. Optimal rates of glucose utilization were obtained when the homogenates were prepared in a K phosphate buffer, pH 7.8, containing KF, and the incubation medium contained the following components (final concns. in brackets): glucose (0.0012-0.0024 [image]); K adenosinetriphosphate (0.005 [image]); MgCl2 (0.005 [image]); KF (0.05 [image]); K phosphate buffer, pH 7.8 (0.04 [image]); KC1 (0.042 [image]). The incubation was conducted in air at 30* and varied from 2 to 16 min. duration. The amt. of glucose utilized was proportional to the volume of homogenate used and in most cases increased linearly with the duration of incubation until at least 80% of the glucose had disappeared. Results, expressed as -Qglucose ([mu]l. glucose disappearing/mg. dry wt. of tissue/hr.) showed that brain (27.1) was the most active tissue and liver (1.4) the least active. A number of tissues were considered in the light of the relationship between their hexokinase activities and their physiological functions.