Evidence for the Existence of meta and para Directing O-Methyltransferases in Tobacco Cell Cultures

Abstract
The O-methyltransferase of tobacco [Nicotiana tabacum] cell culture was resolved to its meta and para directing forms by chromatography on DEAE-cellulose. Despite similarities in molecular weights and pI [isoelectric points] values of the 2 forms, however, evidence from pH optima, SH-group inhibitors, methylation ratios, SDS [sodium dodecyl sulfate]-acrylamide gels and mixed substrate experiments indicates the existence of 2 discrete enzymes acting at the meta and para positions of caffeic acid and quercetin, respectively. The latter enzyme was less substrate specific than its meta counterpart.