elongases

Elongases are a group of enzymes that catalyze the elongation of long-chain fatty acyl-CoA substrates by two-carbon units, producing very long-chain fatty acids (VLCFAs). In animals and fungi, the best-characterized family is the elongation of very long chain fatty acids (ELOVL) enzymes; in plants, elongation is carried out by a set of condensing enzymes in the fatty acid elongation cycle, typically grouped as ketoacyl-CoA synthases (KCS).

Elongation occurs in the endoplasmic reticulum and proceeds by a four-step cycle that adds two carbons from malonyl-CoA to a fatty acyl-CoA, producing a longer acyl chain while releasing CO2. The cycle comprises condensation, reduction, dehydration, and a second reduction, with NADPH supplying the reducing equivalents. Each cycle lengthens the chain by two carbons, yielding saturated and unsaturated VLCFAs depending on substrate availability.

Substrate preference and tissue distribution vary by enzyme family; in mammals the ELOVL family (ELOVL1–ELOVL7) shows distinct specificities for chain length and degree of unsaturation and contributes to lipids such as sphingolipids, skin barrier lipids, myelin, and retinal lipids.

Regulation and clinical relevance: Expression and activity of elongases are influenced by nutrition, hormones, and developmental stage. Alterations in elongase function can affect VLCFA levels and have been linked to metabolic, neurological, and dermatological disorders.

In plants, elongases are part of the fatty acid elongase complex in the endoplasmic reticulum, with KCS enzymes determining seed oil composition and cuticular wax production.

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