JBC, Vol. 250, Issue 15, 5841-5846, Aug, 1975
Alpha hydroxylation of lignoceric acid to cerebronic acid during brain development. Diminished hydroxylase activity in myelin-deficient mouse mutants
S. Murad and Y. Kishimoto
Alpha Hydroxylation of lignoceric acid (n-tetracosanoic acid) to cerebronic
acid (2-hydroxylignoceric acid) by postnuclear preparations of brains from
developing rat, mouse, and several neurological mouse mutants was studied.
The preparations of brains from jimpy and myelin synthesis deficiency (msd)
mice were found to synthesize cerebronic acid at less than 10 percent of
their control rates, and those from quaking and dilute-lethal approximately
30 and 50 percent, respectively. The apparent low rate of in vitro
hydroxylation by brains of the mutant mice appeared to be due to decreased
synthesis rather than increased oxidation of cerebronic acid. Mixing
experiments eliminated the possibility of an inhibitor in the mutant or an
activator in normal animals. The preparations of brains from
wabbler-lethal, ducky, and weaver mice showed normal activity. The
developmental pattern of the hydroxylase activity was examined in quaking,
jimpy, and their control mice. In normal brains the hydroxylase activity
was low in the immediate postnatal period, increased sharply between 10 and
20 days after birth, and fell to a low level following maturation of the
brain. The hydroxylase activity in quaking mice changed similarly during
brain development but at a much reduced level. The brains of jimpy mice had
barely detectable hydroxylase activity which changed little with age and
reached a peak at about 15 days postpartum. The subnormal hydroxylase
activity in brains of quaking mice and the near absence in brains of jimpy
and msd mice correlate with the observations that myelin deficiency is more
severe in jimpy and msd than in quaking. These results suggest a close
association of the synthesis of cerebronic acid with the synthesis of the
characteristic myelin lipid that is cerebroside (N-acyl sphingosine
beta-D-galactoside).