Vitamin C in either the kidney or the liver. In all of the cases where genomic analysis was done on an ascorbic acid auxotroph, the origin of the change was found to be a result of loss-of-function mutations in the gene that codes for L-Gulono-γ-lactone oxidase, the enzyme that catalyzes the last step of the ascorbic acid pathway outlined above. In the case of the simians, it is thought that the loss of the ability to make vitamin C may have occurred much farther back in evolutionary history than the emergence of humans or even apes, since it evidently occurred soon after
Folinic acid to be metabolized in the liver before it could support growth of "L. citrovorum." The synthesis of citrovorum factor by liver cells in culture was eventually accomplished from pteroylglutamic acid in the presence of suitable concentrations of ascorbic acid. The simultaneous addition of sodium formate to such systems resulted in increased citrovorum factor activity in the cell-free supernatants (producing, as now known, the 5-formyl derivative), and from this method of preparation of large amounts of the factor, its structure as levo-folinic acid (5-formyl tetrahydrofolic acid) was eventually deduced. Folinic acid should be distinguished from folic acid (vitamin B). However, folinic