Vitamin B12 (Cyanocobalamin or Cobamide)

 Vitamin B₁₂ (Cyanocobalamin or Cobamide)

(Anti pernicious anaemia factor, Extrinsic factor of Castle)

Introduction

In 1948 Smith and Parker isolated Cyanocobalamin from the liver, In 1955 its complex structure was determined,

Chemistry

The central portion of the molecule consists of four reduced and extensively substituted pyrrol rings surrounding single cobalt atom. The central structure is referred to as a corrin ring. Below the ring system it contains the base dimethyl benziminazole linked with ribose and phosphoric acid.

Properties

·        Red crystalline substance

·        soluble in water

·        contains cobalt (45%)

·        Molecular weight is 1,500

Distribution

Animal sources

·        Liver (1 unit of liver extract contains approximately 1 micro-gram of B₁₂)

·        kidney

·        eggs

·        meat

·        milk

Plant sources

·        Absent

Absorption and excretion

Absorption takes place from the ileum. Intrinsic It is stored in the liver. Vitamin B₁₂ is excreted in the faeces and urine.

Functions

(1) Essential for the formation and maturation of red blood cells.

(2) It plays an essential role in the synthesis of nucleic acid.

(3) Increases the white cell count and the platelets through its action in the bone-marrow.

(4) Concerned with the maintenance of normal health and activity of certain parts of the nervous system.

 (5) Biosynthesis of methyl group is increased by vitamin B12, and this vitamin plays a part in increasing enzymatic rate in one carbon metabolism and synthesis.

(6)This vitamin has also helps in transmethylation process,

(7) Formation of lipid from carbohydrate is influenced by vitamin B12

(9) A coenzyme of vitamin B12 helps in isomerization of glutamic acid to methyl aspartate.

Deficiency signs

(1) Pernicious or macrocytic or megaloblastic anaemia is produced. It brings about hyperglycemia.

(2) Other important features in vitamin B12 deficiency are mucosal atrophy and inflammation of tongue, mouth, etc.

(3) Degenerative lesions of the posterior and lateral columns of the spinal cord.

Daily requirement

A daily intake of 1.0 gm is sufficient to prevent deficiency.