Enantiomeric Form of myo-Inositol-1-Phosphate Produced by myo-Inositol-1-Phosphate Synthase and myo-Inositol Kinase in Higher Plants.

The product of myo-inositol-1-phosphate synthase, EC 5.5.1.4, from mature pollen of Lilium longiflorum Thunb., cv Ace (Easter lily) and that of myo-inositol kinase, EC 2.7.1.64, from wheat germ has been identified as 1l-myo-inositol-1-phosphate by gas chromatography of its trimethylsilyl-methyl phosphate derivative on a glass capillary column bearing a chiral phase.

Evidence that lithium alters phosphoinositide metabolism: chronic administration elevates primarily D-myo-inositol-1-phosphate in cerebral cortex of the rat.

The administration of LiCl (3.6 mequiv./kg/day) to adult male rats for 9 days results in an increase in the cerebral cortex level of myo-inositol-1-phosphate (M1P) to 4.43 +/- 0.52 mmol/kg (dry weight) compared with a control level of 0.24 +/- 0.02 mmol/kg. This establishes that the previously observed acute effect of lithium on M1P (Allison et al., 1976) is both prolonged and augmented by repeated doses of lithium. Larger doses of LiCl over a 3-5 day period result in even larger increases in M1P and a 35% decrease in myo-inositol. In each case, 90% of the increase is due to the D-enantiomer, evidence that lithium is largely producing this effect via phospholipase C-mediated phosphoinositide metabolism. Data are presented showing that lithium is an uncompetitive inhibitor of the hydrolysis of both D- and L-M1P by M1P'ase.