Chain elongation of trans-octadecenoic acid isomers in rat liver microsomes

The chain elongations of trans-octadecenoic acid isomers with double-bond positions delta 4 to delta 15 were studied with rat liver microsomes. The delta 7 and delta 9, trans isomers were converted to trans-9 and trans-11-eicosenoic acids, respectively, at about 40% of the rate of conversion of cis-9-octadecenoic acid to cis-11-eicosenoic acid. The rates of conversion of delta 8, delta 10, delta 11, and delta 12 trans isomers were lower than those of delta 7 and delta 9 trans isomers, but the delta 4, delta 5, delta 6, delta 13, delta 14, and delta 15 trans isomers were not elongated at rates exceeding experimental error.

Effects of dietary vitamin B-2 and vitamin E on the delta9-desaturase and catalase activities in the rat liver microsomes

The effects of dietary vitamin B-2 and vitamin E on delta9-desaturation of stearoyl-CoA, catalase, glutathione peroxidase, superoxide dismutase and electron transport components in rat liver microsomes have been investigated. delta9-desaturase activities were decreased on diets deficient of vitamin B-2, E and supplemented with E. Among the peroxide-scavenging enzymes, only the catalase activity in microsomes correlates significantly with delta9-desaturase activity. In vitro addition of bovine catalase had no effect on microsomal delta9-desaturase activity on control diet. However, it enhanced the delta9-desaturation in microsomes on vitamin B-2-deficient diet which contained low catalase and high superoxide dismutase activities, compared to those in microsomes of control diet. It is suggested that the hydrogen peroxide-generating and -decomposing systems may play an important role on the delta9-desaturase activity in microsomes.