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- *************************************
- * Fatty acid desaturases signatures *
- *************************************
-
- Fatty acid desaturases (EC 1.14.99.-) 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 1.14.99.5) [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 1.14.99.6) [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.
-
- -Consensus pattern: G-E-x-[FY]-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.
-
- -Consensus pattern: [ST]-[SA]-x(3)-[QR]-[LI]-x(5,6)-D-Y-x(2)-[LIVMFYW]-[LIVM]-
- [DE]-x-L
- -Sequences known to belong to this class detected by the pattern: ALL family 2
- enzymes.
- -Other sequence(s) detected in SWISS-PROT: NONE.
-
- -Expert(s) to contact by email: Piffanelli P.
- piffanelli@jii.afrc.ac.uk
-
- -Last update: October 1993 / Patterns and text revised.
-
- [ 1] Kaestner K.H., Ntambi J.M., Kelly T.J. Jr., Lane M.D.
- J. Biol. Chem. 264:14755-14761(1989).
- [ 2] Shanklin J., Somerville C.R.
- Proc. Natl. Acad. Sci. U.S.A. 88:2510-2514(1991).
- [ 3] Wada H., Gombos Z., Murata N.
- Nature 347:200-203(1990).
-