IUBMB Enzyme Nomenclature


Accepted name: inositol-3-phosphate synthase

Reaction: D-glucose 6-phosphate = 1D-myo-inositol 3-phosphate

For diagram click here (mechanism).

Other name(s): myo-inositol-1-phosphate synthase; D-glucose 6-phosphate cycloaldolase; inositol 1-phosphate synthatase; glucose 6-phosphate cyclase; inositol 1-phosphate synthetase; glucose-6-phosphate inositol monophosphate cycloaldolase; glucocycloaldolase; 1L-myo-inositol-1-phosphate lyase (isomerizing)

Systematic name: 1D-myo-inositol-3-phosphate lyase (isomerizing)

Comments: 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.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 9032-95-5


1. Eisenberg, F., Jr. D-Myoinositol 1-phosphate as product of cyclization of glucose 6-phosphate and substrate for a specific phosphatase in rat testis. J. Biol. Chem. 242 (1967) 1375-1382. [PMID: 4290245]

2. Sherman, W.R., Stewart, M.A. and Zinbo, M. Mass spectrometric study on the mechanism of D-glucose 6-phosphate-L-myo-inositol 1-phosphate cyclase. J. Biol. Chem. 244 (1969) 5703-5708. [PMID: 4310603]

3. Barnett, J.E.G. and Corina, D.L. The mechanism of glucose 6-phosphate-D-myo-inositol 1-phosphate cyclase of rat testis. The involvement of hydrogen atoms. Biochem. J. 108 (1968) 125-129. [PMID: 4297937]

4. Barnett, J.E.G., Rasheed, A. and Corina, D.L. Partial reactions of glucose 6-phosphate-1L-myo-inositol 1-phosphate cyclase. Biochem. J. 131 (1973) 21-30. [PMID: 4352864]

[EC created 1972, modified 2001]

Return to EC 5.5.1 home page
Return to EC 5.5 home page
Return to EC 5 home page
Return to Enzymes home page
Return to IUBMB Biochemical Nomenclature home page