Biosynthesis of branched-chain fatty acids from branched-chain amino acids in subcutaneous tissue of the marine little toothed whale, Stenella caeruleo-alba.

1. The conversion mechanism for 14CO2 from [14C]Leu, [14C]Ile and [14C]Val and the incorporation of 14C-amino acids into lipids of subcutaneous tissue (melon and blubber), liver and muscle of the adult whale, Stenella caeruleo-alba were studied using a tissue culture method. 2. Iso-acids such as -5:0, -11:0; -13:0 and -15:0 in melon triglycerides were biosynthesized from [14C]Leu. On the other hand, anteiso-acids such as -5:0, -11:0, -13:0, -15:0 and n-11:0 - n-16:0 acids were derived from [14C]Ile. 3. Iso-acids such as -4:0, -12:0, -14:0 and 16:0 were biosynthesized from [14C]Val. 4. Analytical data indicate that the compositions of these acids biosynthesized were similar to that of fatty acids in whale oil. 5. The branched-chain fatty acid biosynthesized in blubber was iso-5:0 acid from [14C]Leu, with no long-chain branched acids, but n-12:0, -14:0 and -16.0 acids were also biosynthesized. 6. Radioactivities derived from 14C-amino acids incorporated into lipids in liver and muscle were extremely low compared with those in subcutaneous tissue. 7. The ratios of 14C-lipids/14CO2 in every 14C-amino acid incorporation were higher in subcutaneous tissue than in liver and muscle, and especially in the case of [14C]Leu, the ratio in melon was quite high. 8. The incorporation of the 14C-amino acids into short- and long-chain acids and alcohols of wax esters was recognized in all experiments.