The occurrence of direct desaturation of phospholipid acyl chain in Tetrahymena pyriformis. Thermal adaptation of membrane phospholipid.
Microsomes from Tetrahymena pyriformis catalyzed the conversion of 1-acyl-2-[1-14C]oleoyl-sn-glycero-3-phosphorylcholine to 1-acyl-2-[1-14C]linoleoyl-sn-glycero-3-phosphorylcholine in the presence of oxygen and NADH or NADPH as cofactors. This desaturation enzyme activity was inhibited by cyanide and increased by 0.05-0.1% Triton X-100. Under optimal conditions desaturation appeared to follow Michaelis-Menten kinetics with a Km value of 6.9 . 10(-4) M. During incubation, no significant cleavage of phospholipid substrate was observed and no desaturation of free fatty acid occurred. The activity of 1-acyl-2-oleoyl-sn-glycero-3-phosphorylcholine desaturase was increased approx. 4-fold when Tetrahymena cells were shifted to a lower growth temperature. These data suggest the existence of a direct phospholipid desaturation system from oleoylphosphatidylcholine to linoleoylphosphatidylcholine. In addition, this desaturation may participate in the control of membrane lipid adaptation to a lower growth temperature in Tetrahymena.
D000818:Animals; D003486:Cyanides / Q000494:pharmacology; D044943:Fatty Acid Desaturases / Q000378:metabolism*; D008563:Membrane Lipids / Q000378:metabolism*; D009243:NAD / Q000494:pharmacology; D009249:NADP / Q000494:pharmacology; D017830:Octoxynol; D010100:Oxygen; D010713:Phosphatidylcholines / Q000378:metabolism*; D011092:Polyethylene Glycols / Q000494:pharmacology; D013696:Temperature; D013769:Tetrahymena pyriformis / Q000378:metabolism*
D003486:Cyanides; D008563:Membrane Lipids; D010713:Phosphatidylcholines; D009243:NAD; D011092:Polyethylene Glycols; D009249:NADP; D017830:Octoxynol; D044943:Fatty Acid Desaturases; D010100:Oxygen