Biosynthesis of docosahexaenoic acid in trout hepatocytes proceeds via 24-carbon intermediates.
The role of 24:5n-3 and 24:6n-3 as intermediate in the formation of 22:6n-3 in trout liver was examined. Microsomes prepared from trout liver converted [1-14C]-eicosapentaenoic acid (20:5n-3) to 24: 5n-3 and 24:6n-3 but not docosahexaenoic acid (22:6n-3). The radiolabeled 24:5n-3 and 24:6n-3 were isolated from the microsomal incubations by argentation chromatography and used as substrates in incubations with hepatocytes isolated from trout liver. Both 14C-labelled 24:6n-3 and 22:6n-3-were produced by hepatocytes incubated with radiolabelled 24:5n-3. When hepatocytes were incubated with radiolabelled 24:6n-3, the amount of radioactivity recovered in 22:6n-3 over 6 hr increased in direct relation to the decrease observed in the amount of radioactivity recovered in 24:6n-3. The results suggest that the formation of 22:6n-3 in trout liver does not involve delta 4 desaturation of 22:5n-3 but rather proceeds via the delta 6 desaturation of 24:5n-3 with the subsequent chain shortening of the 24:6n-3 produced.
Buzzi
M
M
NERC Unit of Aquatic Biochemistry, Department of Molecular and Biological Sciences, University of Stirling, Scotland, U.K.
Henderson
R J
RJ
Sargent
J R
JR
D000818:Animals; D002250:Carbon Radioisotopes; D004281:Docosahexaenoic Acids / Q000737:chemistry / Q000378:metabolism*; D015118:Eicosapentaenoic Acid / Q000737:chemistry / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000737:chemistry / Q000378:metabolism; D066298:In Vitro Techniques; D008862:Microsomes, Liver / Q000378:metabolism*; D015394:Molecular Structure; D014337:Trout / Q000378:metabolism*
D002250:Carbon Radioisotopes; D005231:Fatty Acids, Unsaturated; D004281:Docosahexaenoic Acids; D015118:Eicosapentaenoic Acid