Studies on plant flavokinase

Abstract

Flavokinase activity has been detected for the first time in plants, and its properties were studied by the application of circular-paper chromatography. The plant investigated was Phaseolus radiatus. Optimum pH for flavokinase activity was 8.6 and temperature 55[degree]C; conversion into flavin mononucleotide was nearly 60%. The Michaelis constant for riboflavin was 0.015 m[image]. Mg++, Zn++ and Mn++ ions showed an activating effect on flavokinase; Zn and Mn ions, however, were inhibitory at higher concentrations. Ca++, Ni++, Li+ and Cd++ ions were without effect. CN-, Hg++, Fe++, Cu++, MnO4 ions and hydroxylamine were inhibitory. A 75-fold purification was obtained by fractionation with ammonium sulfate and adsorption with alumina-C gamma. There was a parallel increase in riboflavin levels and flavokinase activity in germinating seedlings of P, radiatus.