STUDY OF NICOTINE DEMETHYLATION IN NICOTIANA-OTOPHORA

Microsomes from Nicotiana otophora catalyze the demethylation of nicotine to nornicotine in the presence of NADPH and oxygen. Activity was maximal at pH 7.0-7.5 and 30-degrees-C. The enzyme appeared to be most stable in the presence of both nicotine and NADPH. Phosphate, magnesium, nornicotine, and concentrations of microsomal protein higher than 2 mg/mL were inhibitory. Typical rates of nornicotine formation were 10-50 pmol min-1 (mg of protein)-1, while V(max) and the apparent K(m) (nicotine) were estimated to be 105 pmol/min and 51 muM, respectively. Early studies suggest that Triton X-100 may be able to solubilize active nicotine demethylase. Nicotine demethylation satisfies some of the primary criteria for cytochrome P-450 involvement, including inhibition by anticytochrome P-450 reductase, but inhibition by carbon monoxide was not demonstrated.