Rapp. Comm. int. Mer Médit., 36,2001
162
Introduction
The reduced form of glutathione, GSH, is a tripeptide (
?
-glu-cys-
gly) that exists interchangeably with the oxidized form, GSSG. In
plants, the physiological importance may be divided in two categories:
sulphur metabolism and defence. GSH is the predominant non-protein
thiol (1) and it regulates sulphur uptake at root level in the plant. It is
also the precursor of the phytochelatins, which are essential in seques-
tering heavy metals (2). Heavy metal toxicity poses major environ-
mental and health problems. Cadmium, for example, is a non-essential
heavy metal, which is toxic to cells at very low concentrations.
Cadmium ions displace Ca++ or Zn++ in proteins and may cause
oxidative stress (3). Furthermore the concentration of essential, but at
high concentrations toxic, metals such as Cu++, Zn++, Fe++ is strong-
ly controlled. We present data on phytochelatin concentrations in nat-
ural samples of dominant macroalgae species from Thessaloniki Bay,
a body of water under the impact of increasing pollution levels.
Methods - materials
Algae specimens of the dominant species in the Thermaicos Gulf
were collected on a monthly basis from inshore of a heavily industri-
alized area. Reduced, oxidized, and free glutathione and cystein were
determined in algal tissue with post column derivatization with mono-
bromobimane and liquid chromatography.The chromatography sys-
tem was composed of a Hewlett-Packard Series 1100, ?uorescence
detector Hewlett-Packard 1046A and Hewlett-Packard CHEM Station
for LC Version A.04.02 (1996). Chromatography columns for inverse
phase chromatography were packed with 3_m Hypersil ODS at 9000
p.s.i. Heavy metal concentrations in the algal samples were measured
with AAS (6).
Results and discussion
Seasonal variation of the oxidized, reduced and total cystein in
Chlorophyceae showed an inverse pattern. The concentration of the
reduced form was only high during spring 1994.
Reduced and total glutathione exhibited a similar ?uctuation and the
highest concentrations coincided with that of cystein. The oxidized
forms showed the opposite temporal trend.
Environmental conditions caused much higher synthesis of glu-
tathione than cystein in Chlorophyceae where metals accumulated to a
greater degree than in Rhodophyceae (7). Further statistical analysis
(multi-factor linear correlation) showed that 90% of the concentration
variation of all forms of glutathione was due to the combined presence
of Cr, Pb, Cd and Zn. Synthesis of glutathione was even better attrib-
uted to the synchronous effect of Cu, Pb, Cd and Zn and copper ions
were suspected for causing extended production for the peptide (8).
Table 1: Uptake of Pb, Zn, Cu, Cr and Cd and glutathione and
cystein biosynthesis in Chlorophyceae and Rhodophyceae.
Rhodophycea
Chlorophyceae
mean value min-maxSDmean valuemin-maxSD
(µg/g dry wt)
(µg/g dry wt)
Pb3.291-18.333.62Pb3.61.5-5.91.42
Zn3.100.7-7.031.73Zn6.362.7-10.93.04
Cu0.490.15-10.22Cd55.172-1850
Cr552.7253.33-1966531.92Cr477.210-1766547.3
Cd65.94-705149.2Cu683.70.324-10.3
(µg/l)
(µg/l)
Oxy-Cys103.7413.1-456.76111,8
4.51,7-5.641,03
_xy-Glu710.468.9-1928.5497.5
50.1829.7-71.14,6
Tot-Cys5.323.1-566.4175.8
5.31.7-6.31.248
Tot-Glu109470-3213961.3
54.132.6-75.815.96
Red-Cys64.40.1-473144.2
1.250.3-2.010.47
Red-Glu441.21.6-1706.1544.8
3.821.4-5.981.4
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PHYTOCHELATIN SYNTHESIS BY MARINE MACROALGAE LIVING UNDER NATURAL HEAVY METAL
CONCENTRATIONS IN THESSALONIKI BAY, NORTHERN GREECE
Seferlis M.
1*
, S. Haritonidis
2
1
Greek Biotope-Wetland Centre, Thessaloniki, Greece
2
University of Thessaloniki, Sch. of Biology, Dept. of Botany,Thessaloniki, Greece
Abstract
Thioles are sulfuric analogous of alcohols and include phytochelatins (PT) with cystein and glutathione (GSH) being the most common
peptides in plants. When metals (Hg, Pb, Cu) are present, thioles form chelating complexes. Photo-autotrophs are the main entrance for
heavy metals in the trophic chain with humans and animals as the final receivers. Phytochelatins are polypeptides, different from the
metallothioneis (MT) of mammals, and their synthesis is linked to the presence of metals. Biosynthesis of MT is connected to the
metabolism of glutathione, and only limited information exists about their role in macroalgae. An innovative HPLC method for measuring
micromoles of the peptides is presented in this study.
Key words: algae; metals; analytical methods; Greece
Fig. 1: Oxidized, reduced and total cystein and glutathione con-
centration (µmol/l) over time in the dominant Chlorophyceae.
