Studies involving enzymic phosphorylation. 5. The ‘activation’ of rat-brain hexokinase by erythrocyte lysates and muscle extracts*

Studies on hexokinase. 1. The hexokinase activity of rat-brain extracts.

Kinetic studies of the brain hexokinase reaction.

The mechanism of the hexokinase reaction has been the subject of numerous investigations in recent years (l-5). ijgren and Engstrijm reported the incorporation of Pa from labeled adenosine triphosphate (ATP) into the phosphoserine moiety of hexokinase in the absence of substrate glucose and concluded that an enzyme-phosphate intermediate participated in the reaction (2). Gamble and Najjar, howe...

Insulin degradation by human erythrocyte lysates.

In vitro hemolysates of isolated human erythrocytes degrade 125I-labeled insulin. Ten- to 100-fold dilutions of the hemolysate give a proportionately decreased degradation of 125I-labeled insulin at 37 degrees C, while dilutions of up to eightfold do not. Like the control, diluted "Buffer G" containing 5 mmol/L Tris and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid buffer alone, more than ...

Hexokinase type II from rat skeletal muscle.

Kinetic studies with skeletal-muscle hexokinase.

Rat skeletal-muscle hexokinase was partially purified by ammonium sulphate fractionation and gel filtration. The mechanism of the skeletal-muscle hexokinase was studied kinetically by initial-velocity analysis and product inhibition. Glucose 6-phosphate was a non-competitive inhibitor of glucose and ATP. ADP was a non-competitive inhibitor of glucose and a competitive inhibitor of ATP. The data...