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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 1.14.19.1) [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 1.14.19.2) [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.

Piffanelli P.

December 2004 / Pattern and text revised.

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

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

Consensus pattern: G-E-x-[FYN]-H-N-[FY]-H-H-x-F-P-x-D-Y Sequences known to belong to this class detected by the pattern: ALL family 1 enzymes Other sequence(s) detected in Swiss-Prot: NONE.

• Retrieve an alignment of Swiss-Prot true positive hits:   Clustal format, color, condensed view  / Clustal format, color  / Clustal format, plain text  / Fasta format • Retrieve the sequence logo from the alignment • Taxonomic tree view of all Swiss-Prot/TrEMBL entries matching PS00476 • Retrieve a list of all Swiss-Prot/TrEMBL entries matching PS00476 • Scan Swiss-Prot/TrEMBL entries against PS00476 • view ligand binding statistics

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

Consensus pattern: [ST]-[SA]-x(3)-[QR]-[LI]-x(5,6)-D-Y-x(2)-[LIVMFYW]-[LIVM]-[DE] Sequences known to belong to this class detected by the pattern: ALL family 2 enzymes Other sequence(s) detected in Swiss-Prot: NONE.

• Retrieve an alignment of Swiss-Prot true positive hits:   Clustal format, color, condensed view  / Clustal format, color  / Clustal format, plain text  / Fasta format • Retrieve the sequence logo from the alignment • Taxonomic tree view of all Swiss-Prot/TrEMBL entries matching PS00574 • Retrieve a list of all Swiss-Prot/TrEMBL entries matching PS00574 • Scan Swiss-Prot/TrEMBL entries against PS00574 • view ligand binding statistics

Matching PDB structures: 1AFR 1OQ4 1OQ7 1OQ9 ... [ALL]

1	Authors	Kaestner K.H., Ntambi J.M., Kelly T.J. Jr., Lane M.D.
	Title	Differentiation-induced gene expression in 3T3-L1 preadipocytes. A second differentially expressed gene encoding stearoyl-CoA desaturase.
	Source	J. Biol. Chem. 264:14755-14761(1989).
	PubMed ID	2570068

2	Authors	Shanklin J., Somerville C.R.
	Title	Stearoyl-acyl-carrier-protein desaturase from higher plants is structurally unrelated to the animal and fungal homologs.
	Source	Proc. Natl. Acad. Sci. U.S.A. 88:2510-2514(1991).
	PubMed ID	2006187

3	Authors	Wada H., Gombos Z., Murata N.
	Title	Enhancement of chilling tolerance of a cyanobacterium by genetic manipulation of fatty acid desaturation.
	Source	Nature 347:200-203(1990).
	PubMed ID	2118597
	DOI	10.1038/347200a0

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