Developmental regulation of phospholipid methylation in rat brain synaptosomes

Phospholipid methylation was studied in cortical synaptosomes prepared from 7 and 14 day and adult rat brain. Using varying concentrations of [3H] S-adenosylmethionine, Km and Vmax values were determined for the formation of [3H] phosphatidylmonomethylethanolamine (PME), [3H] phosphatidyl-dimethylethanolamine and [3H] phosphatidylcholine (PC). At 25 degree C, the Km values for the formation of all three products, significantly decreased with development. Increasing the temperature to 37 degree C increased the Km values in the 14 day and adult but not the 7 day preparation. The Vmax values at 25 degree C were highest at 7 and 14 days, depending on the product and then decreased in the adult. At 37 degree C, the Vmax values were highest in the 14 day preparation. The overall results are discussed in terms of the developmentally regulated decrease in both synaptic membrane PC and membrane fluidity.