ALTERATION OF MYOINOSITOL MONOPHOSPHATASE IN ALZHEIMERS-DISEASE BRAINS

myo-Inositol monophosphatase (E.C.3.1.3.25) catalyzes the hydrolysis o f myo-inositol 1-phosphate in the presence of Mg2+ at a physiologic pH to form free myo-inositol, maintaining a supply that represents the p recursor for inositol phospholipid second messenger signaling systems. In the present study the activity and protein level of myo-inositol m onophosphatase were investigated in samples from normal human and Alzh eimer's disease (AD) postmortem brains. The separation profile on Seph adex G-100 gel filtration chromatography revealed one major form of my o-inositol monophosphatase in crude extracts from both normal human an d AD brains. In AD brains myo-inositol monophosphatase activity and it s protein level were significantly higher than in control brains. The activity of myo-inositol monophosphatase per enzyme molecule was simil ar in control and AD brains. These results suggest that myo-inositol m onophosphatase is upregulated in AD, probably reflecting compensatory mechanisms concerned with phospholipid metabolism. (C) 1998 Elsevier S cience Ireland Ltd.