J. Wubert et al., HYDROXYBENZOIC ACID METHYLESTERS INHIBIT MAGNESIUM CHELATASE ACTIVITYIN CRESS AND BARLEY SEEDLINGS, Plant physiology and biochemistry, 35(8), 1997, pp. 581-587
The natural compound 3-hydroxybenzoic acid methylester that was found
to inhibit light-dependent chlorophyll synthesis in deetiolated cress
seedlings, also inhibits protochlorophyllide accumulation in dark-grow
n cress seedlings at concentrations >0.1 mM. The isomeric 2-hydroxy an
d 4-hydroxy compounds exhibit inhibition to a similar extent. Accumula
tion of magnesium protoporphyrin that can be observed after incubation
of cress seedlings with 5-aminolevulinic acid, is also inhibited but
accumulation of protoporphyrin is nearly not affected. The conclusion
that magnesium chelatase activity is the point of attack of hydroxyben
zoic acid methylesters was confirmed with barley etioplasts. The enzym
e activitiy was inhibited with K-i = 3.0 mM for 2-hydroxybenzoic acid
methylester, 7.4 mM for 3-hydroxybenzoic acid methylester and 5.4 mM f
or 4-hydroxybenzoic acid methyleter. Chlorophyll accumulation in barle
y seedlings was inhibited in the same concentration range with K-i = 6
.0 mM for 2-hydroxybenzoic acid methylester, 11.0 mM for 3-hydroxybenz
oic acid methylester and 5.0 mM for 4-hydroxybenzoic acid methylester.