Abstract
The Pseudomonas denitrificans coba and the Salmonella typhimurium cbid genes were overexpressed in the heterologous E.coli system. The function of P.denitrificans coba gene product was identified as S-adenosyl methionine dependent methyl transferase catalyzing the C-2 and C-7 methylations of Uroporphyrinogen III to precorrin-2, without performing an extra methylation at C-12 of precorrin-2 to trimethylpyrrocorphin. The function of the S.typhimurium cbid gene product has not yet been identified. The C-terminus of the EColi cysg was shown to be a S-adenosyl methionine dependent methyltransferase catalyzing the C-2 and C-7 methylations of Uroporphyrinogen III to precorrin-2. The C-terminus of cysg was able to perform the extra methylation at C-12 of precorrin-2 to give trimethylpyrrocorphin. The C-terminus of cysg was not involved in the transformation of precorrin-2 to siroheme. The structures of the enzymatic reactions were identified by the use of 13C NMR.
Anousis, Nick (1994). Studies in the biosynthesis of vitamin B12. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1994 -THESIS -A6154.