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 Acid and Lipid Biosynthesis → Fatty Acid Biosynthesis|
Some taxa known to possess this pathway include : Ricinus communis
Expected Taxonomic Range: Viridiplantae
Plant oils contribute significantly to the caloric intake of humans and animals. Vegetable oils are extracted from a number of plant sources, and 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. Laurate 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. Plants contain significant amounts of 2-hydroxy fatty acids in their spingolipids. Oil from Ricinus communis (the source of castor oil) contains almost 90% ricinoleate (D-12-hydroxy-octadec-cis-9-enoate). The compound occurs throughout the plant kingdom, and the enzyme responsible for the hydroxylation (a mixed function oxygenase) shares homology with other fatty acyl desaturases [vandeLoo95]. Ricinoleate is produced in large scale for its use in a variety of compounds. Pyrolyzation of ricinoleate yields sebacic acid, which is used to produce some types of nylon and high temp greases for jet engines.
In developing castor bean, the substrate for the hydroxylase is not the free acid but rather microsomal oleoyl phosphatidylcholine. It requires electron channeling from NADPH to the hydroxylase. Electrons are transferred from NAD(P)H to the site of hydroxylation via a cytochrome b5, similarly to animal stearoyl-CoA desaturase [Smith92a].
Ricinoleate is released from the lipid membrane complex by the action of a specific phospholipase that oxygenates fatty acids.
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
Smith92a: 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
Brown12: Brown AP, Kroon JT, Swarbreck D, Febrer M, Larson TR, Graham IA, Caccamo M, Slabas AR (2012). "Tissue-specific whole transcriptome sequencing in castor, directed at understanding triacylglycerol lipid biosynthetic pathways." PLoS One 7(2);e30100. PMID: 22319559
Lin96: 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
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
©2015 SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025-3493