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: ricinoleic acid biosynthesis
|Superclasses:||Biosynthesis → Fatty Acids and Lipids Biosynthesis → Fatty Acid Biosynthesis → Oleate Biosynthesis|
Some taxa known to possess this pathway include : Ricinus communis
Expected Taxonomic Range: Viridiplantae
Plant oils contribute significantly to the calorie intake of humans and animals. Vegetable oils are extracted from a number of plant sources, soybean oil accounts for nearl 68% of vegetable oil production in the US. Apart from the major use as food, plant oils have several industrial uses. Lauric acid from coconut oil is extensively used in the manufacture of soaps and detergents. The kinds of fatty acid composition in different seed oils determine the quality and use of the oil.
In addition, plants contain significant amounts of 2 hydroxy fatty acids in their spingolipids. In Ricinus communis which is the source of castor oil contains almost 90% ricinoleic acid D-(-)12-hydroxy-octadec-cis-9-enoic acid. This C18 hydroxy fatty acid ricinoleate is a rare one in nature and is particularly abundant in the seed triacylglycerols of castor bean. The fungus Claviceps purpurea which yields Ergot hydroxy fatty acids are found as esterifed to glycerol in triacylglycerols. These extend the ricinoleate molecules through the ester bonds and these lipids are referred to as estolids.
ricinoleate is under large scale production for its use in a variety of compounds. Pyrolyzation of ricinoleate yields sebacic acid, which is used to produce some types of nylon. Sebacic acid also finds use as high temp greases for jet engines.
ricinoleate occurs throughout the plant kingdom however, close relatives of some plants are not able to synthesize ricinoleate. This indicates the ability of synthesize ricinoleate has had multiple independent origins during evolution. Studies have shown that this enzyme shares homology with fatty acyl desaturase [vandeLoo95].
In developing castor bean, microsomal oleoyl phosphatidylcholine is the substrate for the delta 12 hydroxylase. The ricinoleate is released from the lipid membrane complex by the action of a specific phospholipase that oxygenates fatty acids. The delta 12 hydroxylation of oleate to form ricinoleate in developing castor bean is done by a mixed function oxygenase. It requires electron channeling from NADPH to the hydroxylase. The transfer from NAD(P)H to the site of hydroxylation is via cytochrome b5. It is similar to animal stearoyl-CoA desaturase [Smith92].
Broun97: Broun P, Somerville C (1997). "Accumulation of ricinoleic, lesquerolic, and densipolic acids in seeds of transgenic Arabidopsis plants that express a fatty acyl hydroxylase cDNA from castor bean." Plant Physiol 113(3);933-42. PMID: 9085577
Smith92: Smith MA, Jonsson L, Stymne S, Stobart K (1992). "Evidence for cytochrome b5 as an electron donor in ricinoleic acid biosynthesis in microsomal preparations from developing castor bean (Ricinus communis L.)." Biochem J 287 ( Pt 1);141-4. PMID: 1417766
vandeLoo95: van de Loo FJ, Broun P, Turner S, Somerville C (1995). "An oleate 12-hydroxylase from Ricinus communis L. is a fatty acyl desaturase homolog." Proc Natl Acad Sci U S A 92(15);6743-7. PMID: 7624314
Lin96a: Lin JT, McKeon TA, Goodrich-Tanrikulu M, Stafford AE (1996). "Characterization of oleoyl-12-hydroxylase in castor microsomes using the putative substrate, 1-acyl-2-oleoyl-sn-glycero-3-phosphocholine." Lipids 31(6);571-7. PMID: 8784737
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