The Preparation of C4-labeled Biotin and a Study of Its Stability during Carbon Dioxide Fixation by Donald B. Melville,

Several lines of evidence indicate that biotin is involved in the biological fixation of carbon dioxide. Lardy, Potter, and Elvehjem (1) have demonstrated that the biotin requirement of Lactobacillus arabinosus is partially replaceable by oxalacetate and that the growth stimulation of this organism by carbon dioxide is evident only when biotin is present. From microbiological studies with antimetabolites, Shive and Rogers (2) have concluded that biotin is effective in the formation of cr-keto‘glutarate in Escherichiu coli, and in the formation of oxalacetate in L. arabinosus. Lichstein and Umbreit (3) have suggested that biotin is a coenzyme in the oxalacetate decarboxylase enzyme system in E. coli. Ochoa and his coworkers (4) found a decreased activity of the carbon dioxide-fixing “malic” enzyme in livers from biotin-deficient turkeys, whereas livers from folic acid-deficient turkeys were normal in this respect. On the other hand, these workers were unable to identify biotin as a constituent of the purified enzyme. In biotin-deficient rats, Robertson and Lardy (5) have reported a decreased fixation of labeled carbon dioxide in aspartic acid and arginine. While the above studies implicate biotin as an important factor in carbon dioxide fixation, the mechanism involved remains obscure. Based on the structure of biotin and its known chemical reactions, it was early postulated (6) that the vitamin might enter into biological carbon dioxidetransferring mechanisms by virtue of an opening and closing of the ureido ring system. The carbon dioxide thus incorporated into the biotin molecule would then presumably be transferred to pyruvic acid or other substrate concerned in the fixation of carbon dioxide.