Center for Bioinformatics
Oxidoreductases | Transferases | Hydrolases | Lyases | Isomerases | Ligases

Basic Information

Enzyme Number

Official Name

inositol-3-phosphate synthase

Name from literature

l myo inositol phosphate synthase

Pathway from literature

conversion of D-glucose 6-phosphate to L-myo-inositol 1-phosphate in the inositol biosynthetic pathway

Pathway from KEGG

Carbohydrate Metabolism; Inositol phosphate metabolism; map00562

Biosynthesis of Secondary Metabolites; Streptomycin biosynthesis; map00521


Human (9606)

Genome localization

19p13.11[51477 ],


Requires NAD+, which dehydrogenates the -CHOH- group to -CO- at C-5 of the glucose 6-phosphate, making C-6 into an active methylene, able to condense with the -CHO at C-1. Finally, the enzyme-bound NADH reconverts C-5 into the -CHOH- form.

Rate-limiting Description

"DHAP as well as glyceraldehyde 3-phosphate and oxaloacetate inhibited activity of both yeast and human myo-inositol-3 phosphate synthase, the rate-limiting enzyme in de novo inositol biosynthesis." (16221686)

Regulatory Information

Upstream transcription factor


Regulatory type


regulatory enzyme;

"Activity of a putative regulatory enzyme in the biosynthesis of myo-inositol from glucose, ie, glucose 6-P:inositol 1-P cyclase (cyclase), was measured in placenta, fetal lung, and fetal liver. " (6687929)

transcriptional factor;E2F1(1869)

"E2F1 regulation of the human myo-inositol 1-phosphate synthase (ISYNA1) gene promoter." (15464731)

transcriptional factor;E2F1(1869)

"Upregulation occurs through the interaction of several low-affinity E2F binding motifs present in the minimal promoter." (15464731)

transcriptional factor;E2F1(1869)

"E2F1 regulation of the human myo-inositol 1-phosphate synthase (ISYNA1) gene promoter." (15464731)

Gene ontology

Gene ontology

GO:0008654 (P) phospholipid biosynthetic process [Q9NPH2 ];
GO:0004512 (F) inositol-3-phosphate synthase activity [Q9NPH2 ];
GO:0005488 (F) binding [Q9NPH2 ];
GO:0005737 (C) cytoplasm [Q9NPH2 ];
GO:0006021 (P) inositol biosynthetic process [Q9NPH2 ];

Tissue expression

Tissue From HPRD

Thymus [17163 ];
Colon [17163 ];
Leukocyte [17163 ];
Testis [17163 ];
Skeletal muscle [17163 ];
Liver [17163 ];
Brain [17163 ];
Spleen [17163 ];
Prostate [17163 ];
Small intestine [17163 ];
Kidney [17163 ];
Lung [17163 ];
Heart [17163 ];
Pancreas [17163 ];
Ovary [17163 ];
Placenta [17163 ];

Tissue specificity

Highly expressed in testis, ovary, heart, placenta and pancreas. Weakly expressed in blood leukocyte, thymus, skeletal muscle and colon [Q9NPH2 ];

Subcellular localization


cytoplasm [Q9NPH2 ];




Entrez Gene




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  Last Modified: 2009-03-24  
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