Metabolism of 6,9,12-octadecatrienoic acid in the red alga Lithothamnion corallioides: mechanism of formation of a conjugated tetraene fatty acid.
Incubation of [1-14C]6(Z),9(Z),12(Z)-octadecatrienoic acid with an enzyme preparation from the red alga Lithothamnion corallioides Crouan led to the formation of two new compounds, i.e. the conjugated tetraene 6(Z),8(E),10(E),12(Z)-octadecatetraenoic acid and the bis-allylic hydroxy acid 11(R)-hydroxy-6(Z),9(Z),12(Z)-octadecatrienoic acid. These two compounds were formed by independent pathways and were not interconvertible by the enzyme preparation. Experiments with stereospecifically deuteriated 6,9,12-octadecatrienoic acids demonstrated that formation of 6,8,10,12-octadecatetraenoic acid was accompanied by loss of the pro-S and pro-R hydrogens from C-8 and C-11, respectively, whereas formation of 11-hydroxy-6,9,12-octadecatrienoic acid proceeded with loss of the pro-S hydrogen from C-11. Biosynthesis of 6,8,10,12-octadecatetraenoic acid was dioxygen-dependent and was accompanied by production of hydrogen peroxide. A number of artificial electron acceptors supported formation of 6,8,10,12-octadecatetraenoic acid under anaerobic conditions. The existence in Lithothamnion corallioides of a fatty acid oxidase that catalyzes the oxidation of certain poly-unsaturated fatty acids into conjugated tetraene fatty acids is postulated.
Hamberg
M
M
Department of Physiological Chemistry, Karolinska Institutet, Stockholm, Sweden.
D005231:Fatty Acids, Unsaturated / Q000096:biosynthesis*; D006861:Hydrogen Peroxide / Q000378:metabolism; D006880:Hydroxy Acids / Q000378:metabolism*; D008042:Linolenic Acids / Q000378:metabolism*; D010088:Oxidoreductases / Q000378:metabolism*; D000461:Rhodophyta / Q000201:enzymology / Q000378:metabolism*; D013237:Stereoisomerism; D017965:gamma-Linolenic Acid
D005231:Fatty Acids, Unsaturated; D006880:Hydroxy Acids; D008042:Linolenic Acids; C078215:6,8,10,12-octadecatetraenoic acid; C078213:11-hydroxy-6,9,12-octadecatrienoic acid; D017965:gamma-Linolenic Acid; D006861:Hydrogen Peroxide; D010088:Oxidoreductases