Inositol-3-Phosphate Synthase 1 (ISYNA1)

Myoinositol, the most common naturally occurring form of inositol, is a component of plasma membrane phospholipids and functions as a cell signaling molecule. ISYNA1 (EC 5.5.1.4), or IPS, is a rate-limiting enzyme that catalyzes the de novo synthesis of myoinositol 1-phosphate from glucose 6-phosphate. The deduced 558-amino acid protein has a calculated molecular mass of 61.1 kD and shares 66% and 86% identity with yeast and mouse Ips, respectively. Northern blot analysis detected a major 1.8-kb IPS transcript in all tissues examined. Highest expression was in testis, followed by heart, pancreas, and placenta, and lowest expression was in leukocytes, thymus, skeletal muscle, and colon.