Prenatal and postnatal development of protein carboxymethylation activity in the mouse

The carboxymethylation of endogenous methyl-accepting proteins in intact cells of whole embryos decreased between days 9.5 and 11.5 of gestation and thereafter increased. This fluctuation was not due to a change in the level of protein carboxymethylase (PCM) which remained constant during this period. Embryonic PCM was located predominantly in the cytosol of the embryonic cells, as is the case in adult tissues. Brain PCM specific activity was the same as the rest of the body from gestational days 13.5 to 19.5, but thereafter underwent a two- to threefold increase so that by the end of weaning (about 30 days), it had reached the high adult level. This time course suggests that increasing PCM may be part of the brain maturation process occurring during the neonatal period.