Partial Purification and Characterization of S-Adenosyl-L-Methionine: Norreticuline N-Methyltransferases from Berberis Cell Suspension Cultures*
نویسندگان
چکیده
Two new N-methyltransferases (NMT-I and NM T-II) were found to occur in Berberis vulgaris cell suspension cultures. One of these enzymes (NM T-I) was partially purified (100-fold) and characterized. This enzyme is specific for tetrahydrobenzylisoquinoline alkaloids and S-adenosylL-methionine serves as the methyl donor. The apparent molecular weight of the enzyme is 68,000. The pH optimum of the enzyme is 7.6, the temperature optimum 35 °C. Apparent K M values for (/?)-tetrahydropapaverin as substrate were 0.2 m M and for SAM 0.04 m M . The preparation of the same type of enzyme from B. wilsoniae var. subcaulialata was utilized as an efficient enzymatic system for the synthesis of stereochemically pure (/?)as well as (S)-reticuline labelled with tritium or 14C at the N —CH3 group. Enzymes catalyzing this type of reactions are named S-adenosyl-Lm ethionine: norreticuline N-methyltransferases.
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