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°C, the Km values for the formation of all three products, significantly decreased with development. Increasing the temperature to 37°C increased the Km values in the 14 day and adult but not the 7 day preparation. The Vmax values at 25°C were highest at 7 and 14 days, depending on the product and then decreased in the adult. At 37°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.