NMR studies of the enzyme mechanisms of B12

A. I. Scott
1989 Pure and Applied Chemistry  
The active site of porphobilinogen (PBG) deaminase has been enriched with carbon-13 using cells of genetically engineered E . coli. NMR spectroscopy has uncovered the structure of a novel dipyrromethane cofactor, covalently bound through Cys-242, which acts as a nucleophilic site for the covalent binding of substrate. Based on the results of pulse experiments with 13C-enriched S-adenosyl methionine (SAM), the sequence of methylation in the overall conversion of uro'gen 111 to cobyrinic acid is
more » ... Z > C7 > CZO > c 1 7 > C12a > C I > Cs > Cis. These results are incorporated into a mechanistic scheme for comn biosynthesis which also takes into account the discovery of a new series of corphinoids based on the type-I porphyrin template.
doi:10.1351/pac198961030501 fatcat:g55e3q3c4zfdthnol2yfh2aznu