title: Studies on the biosynthesis of the corrin ring of vitamin B 12.
mesh_terms: D003013:Clostridium / Q000378:metabolism*; D003016:Clostridium perfringens / Q000378:metabolism*; D066298:In Vitro Techniques; D007982:Levulinic Acids / Q000378:metabolism; D011166:Porphyrins / Q000096:biosynthesis*; D014805:Vitamin B 12 / Q000096:biosynthesis*
chemical_list: D007982:Levulinic Acids; D011166:Porphyrins; D014805:Vitamin B 12