The utilization of carbon-1 compounds by plants: II. The formation and metabolism of formate by higher plant tissues

Abstract

Tissue slices of carrot root and sunflower cotyledons readily produce formate-C¹⁴ when incubated with glyoxylate-1,2-C¹⁴ and glycine-2-C¹⁴ solutions. Formate-C¹⁴ feeding experiments using a wide variety of higher plant tissues have shown that this compound is readily oxidized to carbon dioxide. This oxidation probably involves a formic dehydrogenase system which has been demonstrated to occur in several of the tissues. Large amounts of formate-C¹⁴ were also incorporated into serine, methionine, and methionine sulfoxide. Degradations of the serine produced from formate-C¹⁴ showed that the bulk of the C¹⁴ was present in the 3 position. The incorporation of formate into serine by radish cotyledons was stimulated under anaerobic conditions and by additions of glycine. Synthesis of methionine and methionine sulfoxide from formate-C¹⁴ was stimulated by additions of homocysteine. The results are interpreted as an indication that formate-C¹⁴ can be oxidized to carbon dioxide by formic dehydrogenase and can serve as a precursor of carbon-1 units that are to be utilized for the biosynthesis of serine and methionine.