“ Biotin has been implicated … deamination of aspartate , serine, and threonine in bacteria in the deamination of serine in animals in the reductive carboxylation of pyruvate by the malic … phosphoenolpyruvate by the phosphoenolpyruvate carboxykinase in carbamylation reactions, in tryptophan metabolism, in purine synthesis, in protein synthesis, and in carbohydrate metabolism.”