A Function for Biotin

During studies on the metabolism of aspartic acid in Escherichia coli it became evident that cells harvested from a complex medium rapidly lost activity and that the lost activity could be restored by the addition of a mixture of the known members of the vitamin B complex. By restricting the conditions of measurement the active agent among these vitamins proved to be biotin, and by separating the various reactions concerned in the comples the biotin was shown to function in oxalacetate decarboxylation. However, some of the evidence available indicates that the natural substrate for this enzyme is not oxalacetic acid as such but a material resembling it, perhaps a phosphorylated oxalacetate. This study represents an unusual mode of obtaining a vitamin deficiency and reveals an unexpected property of biotin. That there existed a relationship between biotin and aspartic acid was shown by Koser, Wright, and Dorfman (1) and Stokes, Larsen, and Gunness (2). The latter workers investigated several of the reactions concerned in the metabolism of aspartic acid and found that biotin was not concerned with transamination. A suggestion that biotin was concerned with the formation of oxalacetate was reported? since oxalacetic acid partially replaced the biotin requirement for some organisms in an asparticdeficient medium. Winzler, Burk, and du Vigneaud (3) found that biotin-deficient yeast cells were markedly stimulated by biotin to take up ammonia.