Inositol-3-phosphate synthase 1

Inositol-3-phosphate synthase 1 (ISYNA1) is the rate-limiting enzyme in myo-inositol biosynthesis, catalyzing the NAD-dependent conversion of glucose 6-phosphate to 1-myo-inositol 1-phosphate (UniProt: Q9NPH2). As the key driver of all inositol-containing compound synthesis, this enzyme plays a fundamental role in cellular phosphoinositide metabolism and signaling.

ISYNA1 is expressed across tissues involved in lipid metabolism and cell signaling. No inherited disease associations are documented in UniProt for this protein.

In Alzheimer's disease, ISYNA1 is significantly upregulated in post-mortem AD brain tissue compared to age-matched controls (Chaparral AD proteomics), with a mean log2 fold-change of 0.93. This upregulation was detected via TMT-labeled quantitative proteomics across subcellular fractions of human brain. The elevated expression may reflect compensatory or pathogenic alterations in phosphoinositide and myo-inositol metabolism in the AD brain.