1021-4437/03/5005- $25.00 © 2003
Russian Journal of Plant Physiology, Vol. 50, No. 5, 2003, pp. 623–626. Translated from Fiziologiya Rastenii, Vol. 50, No. 5, 2003, pp. 699–702.
Original Russian Text Copyright © 2003 by Zaprometov, Nikolaeva.
The vast majority of phenolic compounds are
formed along to the shikimate pathway of biosynthesis,
and initial substrates of their biosynthesis, such as
phosphoenolpyruvate and erythroso-4-phosphate, are
generated in plastids (chloroplasts). At the same time,
phenolic compounds might be synthesized in the cyto-
sol as well, because both the initial substrates and the
isozymes of a number of the shikimate pathway
enzymes were found also in the cytosol [1, 2].
Phenylpropanoid and ﬂavonoid stages of phenolic
compound biosynthesis begin with the deamination of
L-phenylalanine and terminate with the formation of
most monomeric and polymeric phenolic compounds.
Intracellular organization of these stages, as compared
to the shikimate pathway itself, is investigated to a con-
siderably lesser extent. Most of enzymes of the terminal
stages of phenolic compound biosynthesis are cytoso-
lic, and a part of them occur in the microsomal fraction.
Some enzymes are localized in both plastids and cyto-
sol, and this demonstrates that at least some phenolic
compounds can be formed in both of these compart-
Most phenolic compounds after their biosynthesis
are localized in vacuoles and cell walls .
Most enzymes of the phenylpropanoid and ﬂa-
vonoid metabolism were believed to be cytosolic.
Therefore, it was suggested that the cytosol is the site of
phenolic compound biosynthesis, while L-phenylala-
nine formed in chloroplasts is mainly used for protein
The possibility of phenolic compound synthesis in
chloroplasts was ﬁrst demonstrated in young tea leaves.
After their several-min-long exposure to
light, an appreciable incorporation of radioactivity was
found in the catechin (ﬂavan-3-ol) fraction . Subse-
quent investigations using isotope techniques showed
that, in young tea plant and pine shoots, phenolic com-
pounds were formed at a high rate in the course of pho-
tosynthesis [6, 7]. The analysis of photosynthetic prod-
ucts showed that, in the case of polyphenol-rich tea
plant, phenolic compounds accounted for up to 30% of
photosynthate and were exceeded in this respect only
by sugars (45%). However, in the case of pine shoots,
phenolic compounds were exceeded in the label incor-
poration by both sugars and organic acids. It was also
found that tea plant leaf and pine shoot chloroplasts
contained a portion of the phenolic compounds charac-
teristic of these plants. Moreover, chloroplasts isolated
from tea plant leaves, after the exposure of the latter in
the light and in the atmosphere of
, were previ-
ously shown to exceed more than 20-fold in the phe-
nolic compound speciﬁc radioactivity the supernatant
obtained after chloroplast sedimentation .
Such results suggest that chloroplasts are involved
in the phenolic compound synthesis. However, up to
now, it was unclear whether at least a portion of phe-
nolic compounds was synthesized in chloroplasts or the
chloroplasts carried out only some stages of their bio-
synthesis. Therefore, the objective of our further stud-
ies was to solve this problem.
MATERIALS AND METHODS
Ten- to 14-day-old seedlings of kid-
ney bean (
L., cv. Saksa) were used
in this work. They were grown on Perlite in a phytotron
Chloroplasts Isolated from Kidney Bean Leaves Are Capable
of Phenolic Compound Biosynthesis
M. N. Zaprometov and T. N. Nikolaeva
Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya ul. 35, Moscow, 127276 Russia;
fax: 7 (095) 977-8018; e-mail: firstname.lastname@example.org
Received January 23, 2003
—The homogenate and chloroplast fractions isolated from the leaves of 10–14-day-old kidney-bean
L.) seedlings were incubated with
C-L-phenylalanine for 30 min in the light, and the
incorporation of radioactivity into phenolic compounds was determined. Label incorporation into phenolic
compounds of the homogenate and chloroplast fractions amounted to 15–17 and 4–5% of the introduced radio-
activity, respectively. The chloroplasts were about an order of magnitude higher than the homogenate in the spe-
ciﬁc radioactivity of phenolic compounds. Chloroplasts contained four ﬂavonol glycosides (kaempferol and
quercetin aglycones), which were the major components of soluble phenolic compounds of leaves. It was con-
cluded that kidney-bean leaf chloroplasts were capable of performing phenolic compound biosynthesis.
Key words: Phaseolus vulgaris - chloroplasts - phenolic compounds - biosynthesis