Identification of the flavonol 3-OMT enzyme reaction product using Q as the substrate, [14CH3]AdoMet as the cosubstrate, and the Mono-Q fraction II (Fig. 3A) as the enzyme source. A, Autoradiogram of the enzyme reaction product cochromatographed with a reference sample of 3-MeQ on cellulose TLC as desribed in the “Materials and Methods” section. B, HPLC elution profile of reference samples of Q and 3-MeQ. C, HPLC elution profile of the enzyme reaction product showing the residual substrate Q and the product 3-MeQ. The latter exhibits the same retention time and spectral values as the reference compound. D, HPLC elution profile of the reaction products of an enzyme assay lacking the cosubstrate, AdoMet. Notice the lack of substrate utilization or product formation.