INTERACTION OF 5-HYDROXYMETHYL-FURFURAL WITH HYDROXYMETHYLBILANE SYNTHASE

The inhibition of chlorophyll biosynthesis in greening cress seedlings (Lepidium sativum L.) by 5-hydroxymethylfurfural (5-HMF), a natural c ompound isolated from the bulbs of Gladiolus spp. was investigated in vitro and in vivo. A direct reaction between 5-HMF and the chlorophyll precursor porphobilinogen was observed at pH 1.0 but not at pH 8.0. T he enzymatic conversion of porphobilinogen hydroxymethylbilane was inh ibited by 5-HMF with a K-i of about 30 mM. Enzyme kinetics showed that the inhibition was non-competitive. The activity of hydroxymethylbila ne synthase increased during 72 hr development of cress seedlings in d arkness. In the light, there was a further increase of enzyme activity . The light dependent increase in activity was completely abolished wh en the seedlings were incubated with 5-HMF. (C) 1997 Elsevier Science Ltd. All rights reserved.