IUBMB Enzyme Nomenclature


Accepted name: 3-hexulose-6-phosphate synthase

Reaction: D-arabino-hex-3-ulose 6-phosphate = D-ribulose 5-phosphate + formaldehyde

For diagram of reaction, click here

Other name(s): D-arabino-3-hexulose 6-phosphate formaldehyde-lyase; 3-hexulosephosphate synthase; 3-hexulose phosphate synthase; HPS

Systematic name: D-arabino-3-hexulose-6-phosphate formaldehyde-lyase (D-ribulose-5-phosphate-forming)

Comments: Requires Mg2+ or Mn2+ for maximal activity [1]. The enzyme is specific for formaldehyde and D-ribulose 5-phosphate as substrates. Ribose 5-phosphate, xylulose 5-phosphate, allulose 6-phosphate and fructose 6-phosphate cannot act as substrate. This enzyme, along with EC, 6-phospho-3-hexuloisomerase, plays a key role in the ribulose-monophosphate cycle of formaldehyde fixation, which is present in many microorganisms that are capable of utilizing C1-compounds [1]. The hyperthermophilic and anaerobic archaeon Pyrococcus horikoshii OT3 constitutively produces a bifunctional enzyme that sequentially catalyses the reactions of this enzyme and EC, 6-phospho-3-hexuloisomerase [6]. This enzyme is a member of the orotidine 5'-monophosphate decarboxylase (OMPDC) suprafamily [5].

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number:


1. Ferenci, T., Strøm, T. and Quayle, J.R. Purification and properties of 3-hexulose phosphate synthase and phospho-3-hexuloisomerase from Methylococcus capsulatus. Biochem. J. 144 (1974) 477-486. [PMID: 4219834]

2. Kato, N., Ohashi, H., Tani, Y. and Ogata, K. 3-Hexulosephosphate synthase from Methylomonas aminofaciens 77a. Purification, properties and kinetics. Biochim. Biophys. Acta 523 (1978) 236-244. [PMID: 564713]

3. Yanase, H., Ikeyama, K., Mitsui, R., Ra, S., Kita, K., Sakai, Y. and Kato, N. Cloning and sequence analysis of the gene encoding 3-hexulose-6-phosphate synthase from the methylotrophic bacterium, Methylomonas aminofaciens 77a, and its expression in Escherichia coli. FEMS Microbiol. Lett. 135 (1996) 201-205. [PMID: 8595859]

4. Yurimoto, H., Kato, N. and Sakai, Y. Assimilation, dissimilation, and detoxification of formaldehyde, a central metabolic intermediate of methylotrophic metabolism. Chem. Rec. 5 (2005) 367-375. [PMID: 16278835]

5. Kato, N., Yurimoto, H. and Thauer, R.K. The physiological role of the ribulose monophosphate pathway in bacteria and archaea. Biosci. Biotechnol. Biochem. 70 (2006) 10-21. [PMID: 16428816]

6. Orita, I., Yurimoto, H., Hirai, R., Kawarabayasi, Y., Sakai, Y. and Kato, N. The archaeon Pyrococcus horikoshii possesses a bifunctional enzyme for formaldehyde fixation via the ribulose monophosphate pathway. J. Bacteriol. 187 (2005) 3636-3642. [PMID: 15901685]

7. Kato, N., Miyamoto, N., Shimao, M. and Sakazawa, C. 3-Hexulose phosphate pynthase from a new facultative methylotroph, Mycobacterium gastri MB19. Agric. Biol. Chem. 52 (1988) 265-2661.

[EC created 2008]

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