Using a combination of organic chemistry, molecular biology, enzymology, and NMR spectroscopy the details of the biosynthesis of uroporphyrinogen III (the precursor of heme and chlorophyll) and its subsequent transformation to Vitamin B12, the anti-pernicious anemia factor, will be elucidated. Knowledge of the pathway including control mechanisms and genetic mapping will define intermediates important in diseases such as B12 deficiency and porphyria. The mechanisms of several B12 dependent mutases will be studied using NMR spectroscopy of enzymatically enriched substrates. In particular, methyl malonyl CoA mutase, a mammalian enzyme whose deficiency causes metabolic disorder, will be examined in detail and its mode of action determined by a combination of NMR spectroscopy and cryoenzymology. The latter technique is also the method to be used in studying the many enzymes of the pathway from aminolevulinic acid (ALA) to B12.