Characteristics of the oleoyl- and linoleoyl-CoA desaturase and hydroxylase systems in cell fractions from soybean cell suspension cultures

Abstract

Proplastid and microsome fractions of soybean cell cultures showed both Δ 12-desaturase and 3-hydroxylase activities. High thiolase activity for either 18:1-CoA or 18:2-CoA was present in both fractions, but this could be overcome by the addition of ATP, Mg 2+ and CoA. Requirement for NADPH or NADH could not be established conclusively for either enzyme activity; in fact NADH was found to be inhibitory for both enzyme systems. The desaturase and hydroxylase systems were similar to those of other plants with respect to an absolute requirement for oxygen, but differed with respect to their sensitivity to cyanide, which was inhibitory only at very high concentrations. Herbicides such as San 6706 and Destun were strongly inhibitory to both enzyme systems. All metabolic products formed from 18:1-CoA and 18:2-CoA were recovered almost entirely (about 90%) as acyl-CoAs, indicating that the enzyme systems used acyl-CoA as substrate and that acyltransferase activity was low.