Cyanocobalamin interaction

Cyanide is usually found in compounds (substances formed by joining two or more chemicals). Cyanide can interact with metals and other organic compounds (compounds that include carbon). Sodium cyanide and potassium cyanide are examples of simple cyanide compounds. Cyanide can be produced by certain bacteria, fungi, and algae, and is found in a number of foods and plants. In your body, cyanide can combine with a chemical (hydroxocobalamin) to form vitamin B12 (cyanocobalamin). In certain plant foods, including almonds, millet sprouts, lima beans, soy,... 

Interaction with Adenosylcobalamin. It has been considered generally that adenosylcobalamin or its analogs binds to the apoprotein of diol dehydrase or other adenosylcobalamin-dependent enzymes almost irreversibly (4). However, we found that the holo-enzyme of diol dehydrase was resolved completely into intact apoen-zyme and adenosylcobalamin when subjected to gel filtration on a Sephadex G-25 column in the absence of K+ (9, 10). Among the inactive complexes of diol dehydrase with irreversible cobalamin inhibitors, those with cyanocobalamin and methylcobalamin also were resolved upon gel filtration on Sephadex G-25 in the absence of both K+ and substrate, yielding the apoenzyme, which was reconstitutable into the active holoenzyme (II). The enzyme-hydroxocobalamin complex, however, was not resolvable under the same conditions. The enzyme-cobalamin complexes were not resolved at all by gel filtration in the presence of both K+ and substrate. When gel filtration of the holoenzyme was carried out in the presence of K+ only, the holoen-... 

Marchaj, A., Jacobsen, D. W., Savon, S. R., Brown, K. L. (1995). Kinetics and thermodynamics of the interaction of cyanocobalamin (vitamin Bjj) with haptocorrin Measurement of the highest protein-ligand binding constant yet reported, J. Am. Chem. Soc., 117 11640. 

The released CN is transformed into SCN" by a hepatic and renal enzyme, rhodanese [43—45], this sulfuryl transferase being discovered in 1933 [46]. The enzymatic reaction proceeds slowly unless sulfur is supplied and is stimulated by thiosulfate, which is therefore a powerful antidote for CN poisoning. Another antidote is vitamin B12, and results indicate that as plasma cyanide increases the vitamin Bj2 level decreases suggesting that the vitamin may be a cofactor of rhodanese. Vitamin Bj2 will be in the aqua (not hydroxo) form at physiological pH [47], and cyanocobalamin formation is believed to be responsible for the antidotal properties [48—50]. Side effects have also been noted, however, in this connection [43, 51], and low plasma B12 levels may complicate treatment. The direct interaction between nitroprusside and vitamin B12 has been examined by NMR and 1 1 and 1 2 adducts have been observed [47],... 

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