Metabolic Role of Vitamin B12

Abstract

Publisher Summary This chapter discusses the cleavage and synthesis of the carbon-to-cobalt bond and enzyme-catalyzed reactions requiring 5'-deoxyadenosyl cobamides. The enzymatic reactions requiring vitamin B 12 derivatives can be divided into two major groups: (1) those that utilize 5′-deoxyadenosyl-B 12 and involve a hydrogen transfer and (2) those that involve a methyl group transfer, probably via a methyl-B 12 enzyme. The reactions requiring 5′-deoxyadenosyl-B 12 are illustrated and described in the chapter. The chapter describes the role of vitamin B 12 in animal metabolism. Studies with pernicious anemia patients have suggested that vitamin B 12 is required primarily for DNA synthesis, which is essential for the normal development of the mature red blood cell in the bone marrow. In addition, it is well established that there is a nutritional interrelationship among folic acid, vitamin B 12 , and one-carbon metabolism. A summary of various tetrahydrofolic acid derivatives that depicts their role in one-carbon metabolism is illustrated in the chapter. It is observed that tetrahydrofolate is directly involved in the synthesis of purines, thymidylate, and methionine.