The effect of the time in culture of foetal rat neurons and age on the incorporation of radioactive ethanolamine into methylated derivatives was investigated. Decreased incorporation of [3H]ethanolamine into its various methylated water-soluble and lipidic derivatives was observed in rat neurons cultures at 12 day in vitro (DIV) as compared to the 3rd and the 7th DIV. In vivo studies showed that there was a diminished labeling of methylated products in the older animals as compared to the younger ones. These in vitro and in vivo observations suggest a generalized decrease of N-methyltransferase activities during maturation and aging.

Aging↗

PubMedDate not supplied

Factors affecting the stability of detergent-solubilized cholinephosphotransferase and ethanolaminephosphotransferase.

Cholinephosphotransferase (CPT) and ethanolaminephosphotransferase (EPT) are the enzymes catalyzing the last step of the de novo pathway for phosphatidylcholine and phosphatidylethanolamine synthesis, respectively. A major limitation for the complete characterization of the reactions catalyzed by the two enzymes derives from their poor stability in detergent-containing buffers. CPT is heavily inactivated, when native membranes are solubilized using a series of detergents, whereas EPT activity is better preserved during solubilization. An investigation of the factors which could play a role in preserving both enzymes from inactivation was carried out. The dramatic loss of enzymatic activities occurring upon dilution of solubilized membranes with detergent-containing buffers can be reduced by supplementing the dilution medium with phospholipids. The addition of Mn2+ ions to the dispersion buffer increases the stability of both enzymes. The procedure previously described for solubilizing EPT from rat brain microsomes has been modified on the basis of this evidence. Microsomes were solubilized in buffered detergent solutions containing Mn2+ ions and both CPT and EPT were partially purified in their active form by anion-exchange chromatography.

Animals↗