Thioesterase

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Identifiers
EC number	3.1.2
CAS number	9023-79-8
Alt. names
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway

Thioesterase is an enzyme that catalyzes the hydrolysis of thioester bonds, which are a type of ester bond formed between a carboxylic acid and a thiol. Thioesterases play a crucial role in various biochemical pathways, including fatty acid metabolism, polyketide synthesis, and non-ribosomal peptide synthesis.

Function

Thioesterases are involved in the termination of fatty acid synthesis by hydrolyzing the thioester bond between the acyl carrier protein (ACP) and the growing fatty acid chain, releasing the free fatty acid. This reaction is essential for the production of lipids and membrane components in cells.

Types

There are several types of thioesterases, each with specific functions and substrate specificities:

• Type I Thioesterases - These are typically associated with fatty acid synthase complexes and are responsible for releasing the final product of the fatty acid synthesis cycle.

• Type II Thioesterases - These are standalone enzymes that can act on a variety of substrates, often involved in secondary metabolism such as antibiotic production.

• Type III Thioesterases - These are less common and have unique roles in specific biosynthetic pathways.

Mechanism

Thioesterases catalyze the hydrolysis of thioester bonds through a nucleophilic attack on the carbonyl carbon of the thioester linkage. This reaction results in the formation of a carboxylate and a free thiol. The active site of thioesterases typically contains a serine or cysteine residue that acts as the nucleophile.

Clinical Significance

Thioesterases are important in the development of therapeutic agents and biotechnology applications. Inhibitors of thioesterases are being explored as potential drugs for treating metabolic disorders and cancer. Additionally, engineered thioesterases are used in synthetic biology to produce biofuels and bioplastics.

See Also

• Enzyme
• Fatty acid metabolism
• Polyketide
• Non-ribosomal peptide

External Links

• Thioesterase on WikiMD