Utilization of methionine, choline, and beta-methylcholine by Musca domestica larvae

Transfer of the methyl group of methionine to choline and to tRNA in the honeybee Apis mellifica L

Contrary to some previous reports on the absence of biological transmethylation reactions in some insect species, the transfer of the methyl group of methionine-methyl 14C leading to choline and to methylated bases in tRNA was shown in the honeybee Apis mellifica. The addition of antibiotics to the food of the insect does not diminish the incorporation of radioactivity, proving that intestinal bacteria are not responsible for the methylation reactions observed.

On methylating activity of L-(methyl-14C)-methionine in metabolism of phospholipids by insect Ceratitis capitata

The methylating activity of L-(methyl-14C)-methionine in different stages of developmenent of the insect Ceratitis capitata was studied in a series of in vitro and in vivo experiments. Larval and pharate adult homogenates of the insect were used in the in vitro conditions, and the utilization of the methyl group of methionine for the synthesis of different classes of phospholipids was evaluated. Incorporation of radioactivity in lipids by pharate adult homogenates was significantly higher than that by larval homogenates. In both cases, phosphatidyl ethanolamine showed the highest levels of radioactivity incorporation. Free bases from total lipid hydrolysates were resolved and identified by paper chromatography, and the labeling was investigated by radioactivity scanning of paper chromatograms. Significant differences were observed in the activity of both stages of development of the insect. Larval and pharate adult homogenates incorporated mainly the labeled methyl groups into ethanolamine. Monmethyl ethanolamine was the only methyl derivative that appeared in the hydrolysates of lipids synthesized by larval homogenates, whereas mono-,di-and trimethyl ethanolamine clearly were detected in those synthesized by pharate adult homogeneates. Administration of L-(methyl 14C)-methionine to larvae confirmed the existence of methylation reactions in the metabolic activity of the insect.