Thiolase (IPR002155)

Short name: Thiolase

Overlapping homologous superfamilies

Family relationships


Thiolases are ubiquitous enzymes that catalyze the reversible thiolytic cleavage of 3-ketoacyl-CoA into acyl-CoA and acetyl-CoA, a 2-step reaction involving a covalent intermediate formed with a catalytic cysteine. They are found in prokaryotes and eukaryotes. Two different types of thiolase [PMID: 1755959, PMID: 2191949, PMID: 1354266] are found both in eukaryotes and in prokaryotes: acetoacetyl-CoA thiolase (EC: and 3-ketoacyl-CoA thiolase (EC: 3-ketoacyl-CoA thiolase (also called thiolase I) has a broad chain-length specificity for its substrates and is involved in degradative pathways such as fatty acid beta-oxidation. Acetoacetyl-CoA thiolase (also called thiolase II) is specific for the thiolysis of acetoacetyl-CoA and involved in biosynthetic pathways such as poly beta-hydroxybutyrate synthesis or steroid biogenesis.

In eukaryotes, there are two forms of 3-ketoacyl-CoA thiolase: one located in the mitochondrion and the other in peroxisomes.

There are two conserved cysteine residues important for thiolase activity. The first located in the N-terminal section of the enzymes is involved in the formation of an acyl-enzyme intermediate; the second located at the C-terminal extremity is the active site base involved in deprotonation in the condensation reaction [PMID: 15589695].

Mammalian nonspecific lipid-transfer protein (nsL-TP) (also known as sterol carrier protein 2) is a protein which seems to exist in two different forms: a 14 Kd protein (SCP-2) and a larger 58 Kd protein (SCP-x). The former is found in the cytoplasm or the mitochondria and is involved in lipid transport; the latter is found in peroxisomes. The C-terminal part of SCP-x is identical to SCP-2 while the N-terminal portion is evolutionary related to thiolases [PMID: 1755959].

This entry also includes Haloferax mediterranei BktB and phaA with different substrate specificities involved in PHBV biosynthesis [PMID: 23793631]. Their catalytic residues have been identified [PMID: 23793631].

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

GO:0016747 transferase activity, transferring acyl groups other than amino-acyl groups

Cellular Component

No terms assigned in this category.

Contributing signatures

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