Effect of metal ions in the culture medium on the stearoyl-coenzyme A desaturase activity of Mycobacterium phlei.
A particulate fraction prepared from Mycobacterium phlei grown in a metal-deficient medium exhibited a greatly reduced activity of stearoyl-CoA desaturase compared to that from normally grown cells. Metal deficiency, however, had no effect on the FAD-dependent NADPH-cytochrome C reductase activity, which has been suggested to participate in the desaturation process. When the cells were grown in the deficient medium supplemented with both Fe2+ and Mg2+, the desaturase activity was restored to the normal level. Supplementation with Mg2+ alone promoted growth but did not restore the desaturase activity, whereas Fe2+ alone did cause a significant restoration. Among the various metal ions tested, only Fe2+ and Fe3+ enhanced the formation of desaturase activity in the deficient medium. When added to the assay medium in vitro, Fe2+ and Fe3+ did not stimulate the desaturase activity of the particulate fraction from the deficient cells. Cultivation in the metal-deficient medium had essentially no effect on the levels of cytochromes in the particulate fraction, but dramatically decreased the non-heme iron content and the amount of a high-spin ferric species exhibiting an ESR signal at g=4.3. No labile sulfur could be detected in the normal or metal-deficient particulate fractions. It is concluded that the presence of iron ions in the culture medium is necessary for the synthesis and/or assembly of the terminal portion of the desaturase system.
D003470:Culture Media; D044943:Fatty Acid Desaturases / Q000378:metabolism*; D007501:Iron / Q000494:pharmacology*; D008274:Magnesium / Q000494:pharmacology; D008670:Metals / Q000494:pharmacology; D009161:Mycobacterium / Q000201:enzymology*; D009168:Mycobacterium phlei / Q000201:enzymology*; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D013230:Stearoyl-CoA Desaturase / Q000378:metabolism*
D003470:Culture Media; D008670:Metals; D007501:Iron; D044943:Fatty Acid Desaturases; D013230:Stearoyl-CoA Desaturase; D009251:NADPH-Ferrihemoprotein Reductase; D008274:Magnesium