Metabolic fate of cyanocobalamin taken up by Spirometra mansonoides spargana.

Analysis of tissue from Spirometra mansonoides spargana has shown that cyanocobalamin (vitamin B12) is metabolized to adenosylcobalamin and hydroxocobalamin. No methylcobalamin was detected. When the tissues were examined for enzymes which are known to utilize coenzyme forms of vitamin B12, only methylmalonyl CoA mutase, which requires adenosylcobalamin was found. The enzyme, tetrahydropteroylglutamate methyltransferase, which requires methylcobalamin as a cofactor, was not detected. A sizable portion of the cyanocobalamin taken up was bound to ammonium sulfate-precipitable material, suggesting that the binding substance is a protein. Vitamin B12 taken up by spargana was found to be released in vivo with a biological half-life of about 7 weeks.