Isolation and identification of the products of the oxidation of choline.

The results of liver perfusion experiments of Guggenheim and Loeffler (2) suggested that choline is oxidized to betainealdehyde (formylmethyltrimethyl ammonium ion). The products of reactions in vitro (3-6) exhibited the properties of betainealdehyde and betaine. It was shown that these products are formed by two enzymes of rat liver (7), choline oxidase of mitochondria (8, 9), and betainealdehyde dehydrogenase of the cytoplasmic fraction (10, 11). These two enzymes were separated (12) by the technique of differential centrifugation (13), and betainealdehyde dehydrogenase was obtained in a partially purified form from the cytoplasm of rat liver homogenates (11). The syntheses of betainealdehyde (14, 15) and betainealdehyde chloride hydrate (16) had been reported previously. The aldehyde was isolated (17) as the picrate of its 2,4-dinitrophenylhydrazone, identified, and a calorimetric assay method was developed with this derivative as a standard. This assay makes possible the quantitative determination of betainealdehyde and its dehydrogenase, and also of choline oxidase. The present report describes the synthesis, purification, and identification of betainealdehyde chloride hydrate, and the quantitative separation, purification, and identification of the products of the oxidation of choline.