Differences in thermal stability of the fetal and adult brain myoinositol-1-phosphate synthase. Probable involvement of NAD.

L-myo-inositol-1-phosphate synthase (EC 5.5.1.4) from mammalian fetal and adult brain differ considerably with respect to their stability towards different temperatures between 25-65 degrees C. This property has been found to be associated with the presence of the synthase co-factor, NAD, bound to the enzyme protein. The lower thermal stability of the fetal enzyme increases in presence of added NAD (0.8 mM) whereas the higher thermal stability of the adult brain enzyme declines when NAD is specifically removed from the enzyme.