Figure 9.

Monitoring cobalamin and product formation under pre-methylation conditions. Observation of cobalamin species and product generated by pre-methylated MaMmp10 using SAM or d₃-SAM as co-substrates is shown. A and C, quantification of cobalamin species and product formation using SAM as co-substrate. B and D, quantification of cobalamin species and product formation using d₃-SAM as co-substrate. A and B, OHCbl (crosses), MeCbl (closed squares), d₃-MeCbl (open squares). C and D, MeArg product (closed circles) and d₃-MeArg product (open circles). Reactions were performed in triplicate at 30 °C and contained the following in a final volume of 180 μl: 50 mm HEPES, pH 7.5, 200 mm KCl, 40 μm pre-methylated MaMmp 10, 1 mm Ti(III) citrate, and 400 μm peptide substrate. Reactions were initiated with 1 mm SAM or 1 mm d₃-SAM. Error bars denote the standard deviation in the data.