Decreased biosynthesis of saturated C20-C24 fatty acids by the trembler mouse sciatic nerve.

Excised Trembler mouse sciatic nerves synthesize, from acetate, only minute amounts of C20 and C22 saturated fatty acids (about 1 10 of the normal value) and almost no lignoceric acid. The elongation activity is localized in the microsomal fraction. The microsomes from Trembler sciatic nerves can elongate stearoyl-CoA into C20, C22 and C24 saturated fatty acids. The elongation rate is only 1 3 of the normal value, whereas the stearoyl-CoA hydrolysis is 3 times higher than in the control; the malonyl-CoA concentration remains at the same level in microsomes from normal and trembler sciatic nerves. When ATP-Mg(2+) is added to the Trembler microsomes, the stearoyl-CoA hydrolysis is reduced, the stearoyl-CoA concentration remains nearly normal and the elongation reaches an almost normal level.