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.