Competitive Inhibition of Rat Brain Hexokinase by 2-Deoxyglucose, Glucosamine, and Metrizamide |
| |
Authors: | John M Bertoni |
| |
Institution: | Division of Neurology Laboratories, University of Texas Health Science Center at San Antonio, San Antonio, Texas, U.S.A. |
| |
Abstract: | Abstract: The effects of metrizamide on the kinetics of rat brain hexokinase were compared in vitro with those of 2-deoxyglucose and glucosamine. Although metrizamide, 2-deoxyglucose, and glucosamine are known to be competitive inhibitors of approximately equal potency for glucose of yeast hexokinase ( K 1 approximately 0.7 m m for all three), metrizamide is a much weaker competitive inhibitor ( K i about 20 m m ) of rat brain hexokinase than either 2-deoxyglucose or glucosamine ( K i about 0.3 m m for both). This indicates a greater active site specificity of rat brain hexokinase than of yeast hexokinase. Rat brain hexokinase activity is enhanced approximately threefold in the presence of 0.05, 0.2, and 0.8 mg/ml bovine serum albumin, while yeast hexokinase is only enhanced by 50% under these conditions. Despite the high K i value for metrizamide, interference with glucose metabolism may occur whenever metrizamide is present in much higher concentrations than glucose. Myelography in humans is one such situation. |
| |
Keywords: | Metrizamide Glucosamine 2-Deoxyglucose Brain Hexokinase Inhibitor |
|
|