PROSITE documentation PDOC00399
Fatty acid desaturases signatures


Fatty acid desaturases (EC 1.14.19.-) are enzymes that catalyze the insertion of a double bond at the delta position of fatty acids.

There seems to be two distinct families of fatty acid desaturases which do not seem to be evolutionary related.

Family 1 is composed of:

  • Stearoyl-CoA desaturase (SCD) (EC [1]. SCD is a key regulatory enzyme of unsaturated fatty acid biosynthesis. SCD introduces a cis double bond at the delta(9) position of fatty acyl-CoA's such as palmitoleoyl- and oleoyl-CoA. SCD is a membrane-bound enzyme that is thought to function as a part of a multienzyme complex in the endoplasmic reticulum of vertebrates and fungi.

As a signature pattern for this family we selected a conserved region in the C-terminal part of these enzymes, this region is rich in histidine residues and in aromatic residues.

Family 2 is composed of:

  • Plants stearoyl-acyl-carrier-protein desaturase (EC [2], these enzymes catalyze the introduction of a double bond at the delta(9) position of steraoyl-ACP to produce oleoyl-ACP. This enzyme is responsible for the conversion of saturated fatty acids to unsaturated fatty acids in the synthesis of vegetable oils.
  • Cyanobacteria desA [3] an enzyme that can introduce a second cis double bond at the delta(12) position of fatty acid bound to membranes glycerolipids. DesA is involved in chilling tolerance; the phase transition temperature of lipids of cellular membranes being dependent on the degree of unsaturation of fatty acids of the membrane lipids.

As a signature pattern for this family we selected a conserved region in the C-terminal part of these enzymes.

Expert(s) to contact by email:

Piffanelli P.

Last update:

December 2004 / Pattern and text revised.


Technical section

PROSITE methods (with tools and information) covered by this documentation:

FATTY_ACID_DESATUR_1, PS00476; Fatty acid desaturases family 1 signature  (PATTERN)

FATTY_ACID_DESATUR_2, PS00574; Fatty acid desaturases family 2 signature  (PATTERN)


1AuthorsKaestner K.H. Ntambi J.M. Kelly T.J. Jr. Lane M.D.
TitleDifferentiation-induced gene expression in 3T3-L1 preadipocytes. A second differentially expressed gene encoding stearoyl-CoA desaturase.
SourceJ. Biol. Chem. 264:14755-14761(1989).
PubMed ID2570068

2AuthorsShanklin J. Somerville C.R.
TitleStearoyl-acyl-carrier-protein desaturase from higher plants is structurally unrelated to the animal and fungal homologs.
SourceProc. Natl. Acad. Sci. U.S.A. 88:2510-2514(1991).
PubMed ID2006187

3AuthorsWada H. Gombos Z. Murata N.
TitleEnhancement of chilling tolerance of a cyanobacterium by genetic manipulation of fatty acid desaturation.
SourceNature 347:200-203(1990).
PubMed ID2118597

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