Hydroxymethylglutaryl-coenzyme A synthase, N-terminal (IPR013528)

Short name: HMG_CoA_synth_N

Overlapping homologous superfamilies

Domain relationships



Hydroxymethylglutaryl-CoA synthase (EC: catalyses the condensation of acetyl-CoA with acetoacetyl-CoA to produce HMG-CoA and CoA, the second reaction in the mevalonate-dependent isoprenoid biosynthesis pathway. HMG-CoA synthase contains an important catalytic cysteine residue that acts as a nucleophile in the first step of the reaction: the acetylation of the enzyme by acetyl-CoA (its first substrate) to produce an acetyl-enzyme thioester, releasing the reduced coenzyme A. The subsequent nucleophilic attack on acetoacetyl-CoA (its second substrate) leads to the formation of HMG-CoA [PMID: 15498869].

HMG-CoA synthase occurs in eukaryotes, archaea and certain bacteria [PMID: 15546978]. In vertebrates, there are two isozymes located in different subcellular compartments: a cytosolic form that is the starting point of the mevalonate pathway (leads to cholesterol and other sterolic and isoprenoid compounds), and a mitochondrial form responsible for ketone body biosynthesis. HMG-CoA is also found in other eukaryotes such as insects, plants and fungi [PMID: 16640729]. In bacteria, isoprenoid precursors are generally synthesised via an alternative, non-mevalonate pathway, however a number of Gram-positive pathogens utilise a mevalonate pathway involving HMG-CoA synthase that is parallel to that found in eukaryotes [PMID: 17128980, PMID: 16245942].

This entry represents the N-terminal domain of HMG-CoA synthase enzymes from both eukaryotes and prokaryotes.

GO terms

Biological Process

GO:0008299 isoprenoid biosynthetic process

Molecular Function

GO:0004421 hydroxymethylglutaryl-CoA synthase activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.