ALLOXAN-DIABETES ALTERS KINETIC-PROPERTIES OF THE MEMBRANE-BOUND FORM, BUT NOT OF THE SOLUBLE FORM, OF ACETYLCHOLINESTERASE IN RAT-BRAIN

We examined the effects of alloxan-diabetes on the kinetic properties of the soluble and the membrane-bound forms of acetylcholinesterase (A ChE) in rat brain. The K-m (0.15 mM) and V-max. (1.5 mmol/min per mg o f protein) of the soluble form of the enzyme were unchanged in the dia betic animals. The membrane-bound enzyme in the control group displaye d a lower K-m (0.09 mM) and a higher V-max. (7.2 mmol/min per mg of pr otein) compared with the soluble form of the enzyme; the diabetic stat e caused a significant increase (40%) in both K-m and V-max.. K-i(s) v alues were about 3-4 times higher for the membrane-bound enzyme in bot h control and diabetic animals. The results suggest that membrane bind ing and membrane alterations in diabetes can significantly influence t he kinetic properties of AChE.