Cobalamin and folate: recent developments.

Introduction New concepts in this field continue to develop at the clinical level,within the laboratory and in the realm of basic research. The appreciation that the anaesthetic gas nitrous oxide (N20) specifically inactivates the cobalamin dependent enzyme, methionine synthetase, and produces megaloblastic anaemia in man, has made it possible to perform extensive animal studies on cobalamin-folate interrelations, and to test the methylfolate trap hypothesis in a meaningful way. This has led to the development of alternative ideas as to how cobalamin regulates folate metabolism, based on a large body of data obtained from study of animals in which cobalamin was inactivated. Cobalamin neuropathy, too, has been explored in greater depth than has been possible hitherto. On the diagnostic side, considerable claims have been made for the measurement of serum methylmalonic acid as an indicator of cobalamin deficiency.