Assay for vitamin b12 absorption and method of making labeled vitamin b12

Abstract

The invention provides methods for labeling vitamin B12 with 14 C, 13 C, tritium, and deuterium. When radioisotopes are used, the invention provides for methods of labeling B12 with high specific activity. The invention also provides labeled vitamin B12 compositions made in accordance with the invention.

1 . A method for labeling vitamin B12 said method comprising:
 (a) providing a facultative anaerobe bacterium (i) which has a cut operon, (ii) which requires B12 to grow on a medium in which ethanolamine or propandiol is the only carbon source, and (iii) cannot synthesize B12 under aerobic conditions,   (b) providing a medium having ethanolamine or propandiol as the only carbon source,   (c) providing labeled cobinamide (“Cbi”), or a labeled dimethylbenzimidazole (“DMB”), or both, and,   (d) culturing the bacterium on said media in the presence of said Cbi and said DMB, under aerobic conditions,   
       thereby resulting in the formation of labeled B12. 
     
     
         2 . The method of  claim 1 , wherein the bacterium is a  Salmonella  species. 
     
     
         3 . The method of  claim 2 , wherein said  Salmonella  species is  S. enterica.    
     
     
         4 . The method of  claim 1 , wherein said label is selected from the group consisting of  14 C,  13 C, deuterium, and tritium. 
     
     
         5 . The method of  claim 1 , wherein the label is on the DMB. 
     
     
         6 . The method of  claim 1 , wherein the label is  14 C.