physiologits, the term vn B12 is usually a generic name, which includes several related compounds,

deficiency and interrelationship with fohc acid have been described in connection with factors influencing eryrhropoiesis' (chap I11), and will not be repeated here Only such issues, like chemistry and some other relevani points will be taken up as follows Chemistry and nomenclature The letm vit B12 means different things to drllerent persons In the world of organic ch*mislry. it usually means cyanocobalamm (see below} However to the clinicians /pharmacologists/ physiologits, the term vn B12 is usually a generic name, which includes several related compounds, viz. (1) hydroxocobalamin (somvlimes called vrt b12a), (ii) methyl cobalamin, and (111) 5'deoiyadenosyl cobalamrn Another Type of cobalamm is cyanocobalamin, which was the first form of crystallized vil B12 obtained When eiposed lo light. the cyanocobalamin is automatically convened mlo hydronocobalamm The term wit B12 also includes cyanocobalarnm However, today, in 1992, most authors are using vit B12 and cyafiocobalamin as interchange able terms Dietary vit B12 is usually the 5'deoxy adenoey1 cobalamm. methyl cobalamin it the Form of vrt 612 m which ii circulates m the blood Hydrono cobalamin is (he form which is obtained when other forms of cobalamms are exposed to lighl Besides, Ihe mjectible vrt Bl? also is hydroiio cobalamm A tobalarrin is a compound which contain? two parts, viz. (i) • 'com n1 nucleus having a strong similarity with porphynn, but a cobalt atom lies at the center instead o an iron' atom as in heme and (ii) a nucleotide The names of different cobalamins are sell explanatory, thus hydroiy or methyl ccbalamm means when OH or CH3 group is attached to the cobalt atom A representative structure of cobalemin is shown below (fig. 7 US) Foe her works on ths chemistry of vn B12 Dorothy Hodgkin wis awarded Nobel Pnze in 1964 Fig 7 14 5 Deficiency Lack of vrt B12 causes inhibition