Rapp. Comm. int. Mer Médit., 36,2001
202
Introduction
Phospholipases A2 (PLA2) form a large family of lipolytic enzymes (1).
PLA2 is a major component of snake and other venoms, digestive secre-
tions of the gastrointestinal tract, as well as secretions of various mucous
surfaces including tears and seminal ?uid. In addition to toxic and diges-
tive functions, PLA2 has effective bactericidal properties and participates
in the regulation of in?ammation by releasing arachidonic acids from cel-
lular membrane phospholipids for eicosanoid synthesis. The purpose of the
current study was to investigate the occurrence of PLA2 in marine inverte-
brate tissues.
Material and methods
Specimens were collected at 0-20 m depth from the Great Barrier Reef,
Northern Queensland, Australia. Samples were immersed in 50 mM
acetate buffer, pH 5, containing protease inhibitors, and frozen at -18°C.
After thawing, the specimens were homogenised by Ultra Turrax or shak-
en vigorously in a glass container (coral specimens) and centrifuged at 5
000 g. The supernatants were assayed for PLA2 activity by using 14C-
labelled phosphatidylcholine in mixed micelles as a substrate. Protein was
determined by a standard dye-binding assay.
Results and discussion
The highest PLA2 activities were found in the extracts of hard coral, fire
coral, crown-of thorns starfish and sea cucumber (Table 1). The high PLA2
content in the puffer fish intestine is similar to mammalian intestine where
the enzyme is expressed in mucosal Paneth cells (2). High PLA2 activities
were found in a number of echinoderms and sea anemones, whereas the
annelids, crustaceans and molluscs tested had relatively low PLA2 activi-
ty.The functions of PLA2 in invertebrates are not well known. The action
of PLA2 on phospholipids initiates the synthesis of eicosanoids present in
most animal species including invertebrates (3). Insect immune response to
bacteria is mediated by eicosanoids (4). PLA2 activity has been reported in
the granular amebocytes, important immunocompetent cells of the horse-
shoe crab, Limulus polyphemus(5). PLA2 is a well-characterised digestive
enzyme in mammals (1). Digestive PLA2s have been found in the tiger bee-
tle Cicindella circ
u
m
p
i
c
t
a(6) and the starfish Asterina pectinifera(7). T
h
e
presence of PLA2 in snake venoms has been known since the 1890’(1) and
has been reported in numerous invertebrate venoms including that of the
marine snail Conus mag
u
s(8), the scorpion Pandinus impera
t
o
r(9), the ant
P
s
e
u
d
o
m
y
r
m
ex triplarinus(10), the sea anemone Aiptasia pallida(11) and
the jellyfish Rhopilema nomadica(12). It is pertinent that the highest leve
l
s
of PLA2 observed in echinoderms in the present study were found in tissues
that are associated with toxins; E
.
G
.the spines of the crow
n
-
o
f
-
t
h
o
r
n
s
s
t
a
r
fish have a powerful neurotoxin. Pyloric cecae of echinoderms contain
PLA2 that may function as a digestive enzyme.
The current results demonstrate the presence of PLA2 activity in a num-
ber of marine invertebrates. The molecular structure, classification and
physiological functions of these PLA2s remain to be studied.
References
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201-208.
3- Stanley-Samuelson D.W., 1991. Comparative eicosanoid physiology in
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H.H. and Possani L.D., 1997. The mechanism of inhibition of ryanodine
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Pandinus imperator. J. Biol. Chem.272: 11886-11894.
10- Hinks W.F., Pappas P.W. and Jaworski D.C., 1994. Partial biochemical
characterization of venom from the ant, Pseudomyrmex triplarinus. Toxicon
32:763-772.
11- Grotendorst G.R. and Hessiger D.A., 2000. Enzymatic characterization of
the major phospholipase A2 component of sea anemone (Aiptasia pallida)
nematocyst venom. Toxicon38: 931-943.
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nomadica.Toxicon35: 637-648.
PHOSPHOLIPASE A2 IN MARINE INVERTEBRATES
Timo J. Nevalainen
1
*, Lyndon E. Llewellyn
2
and John A. H. Benzie
2,3
1
Department of Pathology, University of Turku,Turku, Finland
2
Australian Institute of Marine Science, Townsville, Queensland, Australia
3
Centre for Marine and Coastal Studies, University of New South Wales, Sydney,Australia
Abstract
Phospholipase A2 (PLA2) catalytic activity was determined by a radiochemical assay in tissue extracts from 21 species belonging to five phyla of
marine invertebrates that were collected from the Great Barrier Reef, Queensland, Australia. The highest PLA2 activities were found in hard coral,
fire coral, crown-of thorns starfish and sea cucumber. High PLA2 activities were found in a number of echinoderms and sea anemones, whereas
annelids, crustaceans and molluscs contained relatively low amounts of PLA2 activity.The results demonstrate the presence of PLA2 activity in a
number of marine invertebrates. The molecular structure, classification and physiological functions of these PLA2s remain to be studied.
Key words : Cnidaria, echinodermata, mollusca, toxins
U/g (SD)n
Cnidaria
Soft coral
Sinularia ?exibilis
22 (6)2
Soft coral
Sarcophyton elegans
82 (91)4
Soft coral
Dendronephthya sp.
64 (12)10
Hard coral
Acropora
sp.
267
1
Hard coral
Pocillopora damicorni
s
945 (540)10
Hydrozoan fire coral
Millepora
sp.
735
1
Sea anemone
Stoichactis
sp.
207 (35)2
Sea anemone
Actinia australis
90 (24)2
Annelida
Worm
Phyllodoce novaehollandiae
29 (32)4
Crustacea
Ghost crab
Ocypode cordimana
3 (2)7
Prawn
Panaeus monodon
Hepatopancreas
52 (79)3
Muscle
0.5 (0.2)2
Mollusca
Rock-oyster
Saccostrea cuccullata
1
1
Clam
Donax cuneatus
2 (1)6
Nudibanch
Phyllida
sp.
65
1
Echinodermata
Crinoid
Colobometra perspinosa
124
1
Brittle star
Ophiocoma erinaceus
Disc
33
1
Arm
29
1
Starfish
Gomophia
sp.
253
1
Starfish
Fromia
sp.
288
1
Starfish
Linckia laevigata
244
1
Crown-of-thorns starfish
Acanthaster planci
Skin
97
1
Spines
16251
Body wall
117
1
Pyloric ceca
498
1
Sea cucumber
Stichopus chloronotus
Body wall
54231
Intestine
235
1
Rete mirabile
614
1
Vertebrata
Pufferfish
Arothron manilensis
Skin
177 (87)5
Muscle
4 (2)5
Liver
78 (73)5
Intestine
2753 (1058)5
Table 1. Phospholipase A2 activity concentration (U/g protein)
in tissue extracts. Where a specific tissue is not indicated the
assay was undertaken on whole animal extract.
