This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Synonyms: Δ5-eicosenoic acid biosynthesis
|Superclasses:||Biosynthesis → Fatty Acid and Lipid Biosynthesis → Fatty Acid Biosynthesis → Unsaturated Fatty Acid Biosynthesis|
Expected Taxonomic Range: Magnoliophyta
Oleate (18:1Δ9) is the most commonly found mono-unsaturated fatty acids in plant oils. However a number of other mono-unsaturated fatty acid species are naturally accumulated in some plants. The seed oil of Limnanthes alba (meadowfoam) has high content of Δ5 unsaturated C20 and C22 fatty acids, with (5Z)-icos-5-enoate (20:1Δ5) accounting for 60% of the total fatty acids. The high content of (5Z)-icos-5-enoate makes the meadowfoam seed oil desirable for use in cosmetics, surfactants and lubricants.
The biosynthesis of Δ5-eicosenoate biosynthesis in Limnanthes alba has several novel features. Firstly, the elongation step, which is catalyzed by saturated fatty acid-specific FAE1, starts with palmitate (16:0) instead of stearate (18:0) or oleate (18:1). The latter two serve as the initial substrates for very long chain fatty acids biosynthesis in most plant species [Pollard80].
Secondly, the Δ5 double bond is introduced by an acyl-CoA desaturase [Moreau81, Cahoon00]. Acyl-CoA desaturation is the major route of monounsaturated fatty acid synthesis in animals and fungi, but is rarely found in plants, which usually use either an acyl-[acp] desaturase or an acyl-lipid desaturase (which act on fatty acids bound to coenzyme A or glycerol lipids, respectively, as substrates).
Cahoon00: Cahoon EB, Marillia EF, Stecca KL, Hall SE, Taylor DC, Kinney AJ (2000). "Production of fatty acid components of meadowfoam oil in somatic soybean embryos." Plant Physiol 124(1);243-51. PMID: 10982439
Moreau81: Moreau RA, Pollard MR, Stumpf PK (1981). "Properties of a delta 5-fatty acyl-CoA desaturase in the cotyledons of developing Limnanthes alba." Arch Biochem Biophys 209(2);376-84. PMID: 7294800
Pollard80: Pollard MR, Stumpf PK (1980). "Biosynthesis of C(20) and C(22) Fatty Acids by Developing Seeds of Limnanthes alba: CHAIN ELONGATION AND Delta5 DESATURATION." Plant Physiol 66(4);649-55. PMID: 16661496
King07: King A, Nam JW, Han J, Hilliard J, Jaworski JG (2007). "Cuticular wax biosynthesis in petunia petals: cloning and characterization of an alcohol-acyltransferase that synthesizes wax-esters." Planta 226(2);381-94. PMID: 17323080
Napier03: Napier JA, Michaelson LV, Sayanova O (2003). "The role of cytochrome b5 fusion desaturases in the synthesis of polyunsaturated fatty acids." Prostaglandins Leukot Essent Fatty Acids 68(2);135-43. PMID: 12538077
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