Biosynthesis of L-ascorbic acid: missing steps in animals incapable of synthesizing the vitamin.

Abstract

IT has been reported1 that cyanide greatly stimulates the synthesis of L-ascorbic acid from D-glucuronolactone by the liver microsomes of the rat. By this method using cyanide it was found that either the liver or the kidney tissue of all the species examined which are known to be independent of an exogenous source of ascorbic acid was able to synthesize L-ascorbic acid, while the corresponding tissue of those which are dependent on such a source could not. Whether the enzyme system concerned was present in the liver or the kidney tissue depended on the position of the species in the phylogenetic scale of evolution2. This technique revealed further that, apart from man, monkey and the guinea pig, the India fruit bat (Pteropus medius) and the redvented bulbul (Pycnonotus cafer) were unable to synthesize L-ascorbic acid, and this was confirmed by the production of experimental scurvy in the bulbul and its cure by the administration of L-ascorbic acid3. This communication concerns the location of the genetic defect in all these species, which distinguishes them from those which can synthesize L-ascorbic acid.