The effect of dietary sterol on the activity of fatty acid desaturases isolated from Tetrahymena setosa.
Tetrahymena setosa has a nutritional requirement for micro amounts of sterol, a requirement which is also satisfied by relatively large amounts of either intact phospholipids or a mixture of unsaturated fatty acids normally found in these ciliates. Three microsomal fatty acyl-CoA desaturases have been isolated from T. setosa and partially characterized. These enzymes which can account for the formation of the majority of the ciliate's unsaturated fatty acids, include: a delta 9, a delta 12 and a delta 6 desaturase which catalyze the transformation of stearoyl-CoA to oleic acid, of oleoyl-CoA to linoleic acid and of linoleoyl-CoA to gamma-linolenic acid, respectively. The stearoyl CoA desaturase required NAD (or NADP), ATP and free CoA; the delta 6 and delta 12 desaturases required NADP, but not ATP or CoA. Cellular levels of the three desaturases were highest in mid-logarithmic phase cells and lowest in stationary phase cells. In order to determine if there was a relationship between the sterol requirement and the ability of the organism to desaturate, T. setosa was grown in a synthetic medium supplemented with either cholesterol or a phospholipid which permits growth in the absence of cholesterol, or with both phospholipid and cholesterol. Cells grown with phospholipid alone had only half as much stearoyl-CoA and oleoyl-CoA desaturase activity as cells of identical culture age grown either on cholesterol alone or on cholesterol plus phospholipid.
Koll
M
M
Chicago Board of Health, Daley Center, Illinois 60602.
Erwin
J A
JA
D000214:Acyl Coenzyme A / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002849:Chromatography, Gas; D003067:Coenzymes / Q000378:metabolism; D003653:Decarboxylation; D004041:Dietary Fats / Q000494:pharmacology*; D044943:Fatty Acid Desaturases / Q000302:isolation & purification / Q000378:metabolism*; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D013261:Sterols / Q000494:pharmacology*; D013768:Tetrahymena / Q000201:enzymology*
D000214:Acyl Coenzyme A; D003067:Coenzymes; D004041:Dietary Fats; D013261:Sterols; D009243:NAD; D009249:NADP; D000255:Adenosine Triphosphate; D044943:Fatty Acid Desaturases