Byerrum Et Al-betaine as a Methyl Donor

methvlation can occur. It was found that after feeding choline-methyl-C14 to plants, radioactive betaine and dimethylglycine had been produced. Choline could give rise to betaine either by transferring its methyl groups to glycine, or some methylated glycine, to yield betaine, or oxidation of choline to betaine could occur. The experiments of Cromwell and Rennie (5) and of Bregoff and Delwiche (1) seem to inclicate that betaine is synthesized in two species of higher plants largely through oxidation of choline and not by methylation of glycine. This finding would suggest that the radioactive betaine found in tobacco plants after feeding radioactive choline resulted from oxidation of choline. If this assumption is correct, the dimethylglycine would arise from betaine which had transferred one of its methyl groups. No radioactive dlemethylation product of choline wa.s (liscovered. An attempt was made to demonstrate choline oxidase activity in various preparations from tobacco leaves ain(l roots but thus far this has been uinsuccessful. Although none of the observations in themselves prove that choline must be oxidized to betaine before methvlation can occur, the bulk of experiments indicate that in higher plants choline may yield its methyl groups only upon conversion to betaine, btit fuirther work will be needed to settle the point.