4-hydroxy-3-methylbut-2-en-1-yl diphosphate synthase

In enzymology, a 4-hydroxy-3-methylbut-2-en-1-yl diphosphate synthase (HMB-PP synthase, IspG, EC 1.17.7.1) is an enzyme that catalyzes the chemical reaction

2-C-methyl-D-erythritol 2,4-cyclodiphosphate + protein-dithiol ${\displaystyle \rightleftharpoons }$ (E)-4-hydroxy-3-methylbut-2-en-1-yl diphosphate + H₂O + protein-disulfide

4-hydroxy-3-methylbut-2-en-1-yl diphosphate synthase
Identifiers
EC no.	1.17.7.1
Databases
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway
PRIAM	profile
PDB structures	RCSB PDB PDBe PDBsum
Gene Ontology	AmiGO / QuickGO
Search PMC articles PubMed articles NCBI proteins

The substrate of this enzyme is 2-C-methyl-D-erythritol 2,4-cyclodiphosphate (MEcPP) and the product is (E)-4-hydroxy-3-methylbut-2-en-1-yl diphosphate (HMB-PP). Electrons are donated by two reduced ferredoxin proteins per reaction.

This enzyme participates in the MEP pathway (non-mevalonate pathway) of Isoprenoid precursor biosynthesis.

Nomenclature

This enzyme belongs to the family of oxidoreductases, specifically those acting on CH or CH₂ groups with a disulfide as acceptor. The systematic name of this enzyme class is (E)-4-hydroxy-3-methylbut-2-en-1-yl-diphosphate:protein-disulfide oxidoreductase (hydrating).