Metabolism of odd-numbered, normal fatty acids in Tetrahymena pyriformis W

Abstract

Tetrahymena pyriformis W cells were grown with short- and long-chain, odd and even normal fatty acid supplements. Tris acetate addition had no effect on the fatty acyl composition of the glycerophospholipids or sphingolipids, while Tris propionate supplementation led to a marked increase in odd normal fatty acids at the expense of even normal acids in both classes of complex lipids. This enhancement of odd normal acids permitted the identification of 17 : 1 Δ 9( n), 17 : 2 Δ 6,9( n), 17 : 2 Δ 9,12( n), 17 : 3 Δ 6,9,12( n), 19 : 1 Δ 9( n), 19 : 2 Δ 9,12( n) and 19 : 3 Δ 6,9,12( n) by oxidation with periodate-permanganate and examination of the short-chain fragments. Supplementation with pentadecanoic acid (15 : 0( n)) led to an increase in the proportions of normal C 15, C 17 and C 19 acids. The increase in C 15 acids primarily reflected a rise in 15 : 0( n), whereas the rise in the levels of C17 and C 19 acids was accounted for by an elevation of unsaturated acids. Growth with heptadecanoic acid (17 : 0( n)) resulted in substantial increases in unsaturated normal C 17 and C 19 fatty acids, while nonadecanoic acid (19 : 0( n)) addition led only to an increase in the proportion of unsaturated C 19 acids. Retroconversion of these saturated, odd normal long-chain fatty acid supplements was limited. Supplementation with arachidic acid (20 : 0( n)) resulted in only a marginal increase (1.4%) in normal C 20 fatty acids of both the glycerophospholipids and the mild alkali labile neutral lipids and provided no evidence that desaturation occurred. The release of 14CO 2 from [1− 14C] arachidic acid when incubated with the ciliates indicated that this long-chain saturate is accumulated, activated and degraded. Normal C 16−C 19 saturated fatty acids are substrates for the Δ 9 desaturase. The Δ 11 isomers arise by chain elongation. Normal C 16–C 19 Δ 9 monoenoic acids are substrates for the Δ 12 desaturase. Normal C 16–C 18 Δ 9 monoenes, normal C 16–C 19 Δ 9,12 dienes and 18 : 1 Δ 11( n) are desaturated at the C-6,7 position.