Explain about the Cyanocobalamin (vitamin B₁₂)?

Vitamin B₁₂ (cobalamin, cbl) is a unique vitamin in human nutrition, since its malabsorption leads to the fatal syndrome of pernicious and megaloblastic anaemias with demyelinating lesions of the central nervous system. The structure of vitamin B₁₂ is shown earliar. As you may have noticed, vitamin B₁₂ is the largest of the B complex vitamins. It consists of a corrin ring made up of four pyroles with cobalt at the centre of the ring. There are several vitamin B₁₂-dependent enzymes in bacteria and algae, but no species of plants have the enzymes necessary for vitamin B₁₂ synthesis.