Metabolism of Choline and Related Compounds by Hepatic Tissue From Several Species Including Man.

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Abstract
Data on the activity of choline oxidase, succinoxidase, tributyrinase, and the enzymes concerned in the formation of methionine from choline, betaine or dimethylthetin, and homocysteine are presented for liver tissue from the rat, mouse, guinea pig, rabbit, chicken, dog, and man. The analysis of 3 samples of fresh human liver indicates that man resembles the rabbit and guinea pig in that choline oxidase activity and the capacity to utilize choline to methylate homocysteine are low or absent. In contrast, the livers of all species examined were capable of utilizing betaine and its sulfur analog, dimethylthetin, to methylate homocysteine to form methionine. Succinoxidase activity of 4 samples of fresh human liver was markedly lower than that of the other species examined. Tributyrinase activity of 2 samples examined was of the same order of magnitude as that found in livers from the rat and the mouse.