Abstract
When watercress is kept in a dilute phosphate buffer of pH 7.0 containing 0.2mg% of riboflavin according to the procedure of water culture in the dark, a factor capable of decomposing riboflavin is induced in every part of the plant after several days, and the factor partly comes out into the medium from roots. This riboflavin-decomposing factor is heat-labile and composed of two parts, which are separable by dialysis. The factor decomposes riboflavin optimally at pH 7.0〜7.2 and 25℃. The decomposition of riboflavin by this factor was not affected by some enzyme inhibitors tested (final concentration, 2×10^<-5>M), such as cyanate and monoiodoacetate, except malonate which somewhat retarded the reaction. By these observations, it is supposed that the riboflavin-decomposing factor is an enzyme. No fluorescent degradation product was detected by paper chromatography in plant factor-riboflavin reaction mixtures.
