546
14 Glycolysis
tions and can easily switch from lactate production to lactate oxidation. This distribution of
isoenzymes of D-specific LDH allows a division of
labour between the musculature and the other tissues just like that found for the L-specific LDHs
of the vertebrates and the isoenzymes of octopine
dehydrogenase in the cephalopods [27, 70].
Isoenzymes of D-specific LDH are also found in
various gastropods but probably not as part of a
complex adapted system like that of Limulus
[183].
14.11.3 Opine Dehydrogenases
To date, five different opine dehydrogenases have
been described (Fig. 14.5). The first to be characterized, in 1959, was the opine dehydrogenase
from various molluscs and Sipunculus nudus; this
was followed in 1976 by the alanopine/strombine
dehydrogenase of the oyster Crassostrea gigas, in
1985 by the tauropine dehydrogenase of the snail
Haliotis lamellosa, and in 1987 by the ~-alanopine
dehydrogenase of the mussel Scapharca broughtonii. It is quite possible that further enzymes of
this type exist. As well as in the molluscs, octopine dehydrogenases (ODH) have since been
reported in sea anemones, nemertines, sipunculids, and brachiopods and have, in part, been characterized; in the annelids, they have as yet been
detected only in the polychaete Glycera lapidum.
The distribution of ODH amongst the molluscs is
by far the best documented. They are probably
present in all cephalopods. In the gastropods,
they are widely found in the prosobranch neogastropods as well as in several aracheo- and
mesogastropods, but not in the opisthobranchs or
pulmonates. ODHs are widely distributed in both
marine and freshwater mussels with the exceptions of the families Ostreidae and Myidae. Alanopine and strombine dehydrogenases are usually
found together in the poriferans, cnidarians,
nemertines, sipunculids, brachiopods, annelids
and mussels; in the molluscs, they are absent
from the cephalopods, gastropods, nudibranchs
(opisthobranchs) and all freshwater species
[68, 84, 140]. Tauropine dehydrogenase not only
is found in all species of the genus Haliotis but has
also recently been isolated from the stem of the
brachiopod Glottidia pyramidata [47, 69, 218]. ~Alanopine and the corresponding dehydrogenase
are only known so far in the mussel Scapharca
broughtonii [219].
All known opine dehydrogenases are monomeric proteins of about 35-40 kDa [47, 69,
70, 190, 242]. The similarities of the molecular
masses and catalytic properties make it likely that
all opine dehydrogenases are homologous,
although this awaits confirmation from sequence
data. It is already clear that there is no immunological relationship between ODH and other pyruvate dehydrogenases, and that ODH apparently
has a very high rate of evolution; antibodies
against ODH of the eight-armed cephalopod
Haplochlaena maculosa cross-react with the
ODH of all octopods but react only weakly with
the enzyme of all other cephalopods and not at all
with the enzyme of mussels and snails [70].
The reactions of the ODHs from the marine
molluscs Pecten maximus and Concholepas concholepas have been examined in detail. In the forward reaction, NADH is bound first, followed
randomly by arginine and pyruvate, whereas in
the reverse reaction first NAD+ is bound and
then octopine [28]. In the substrate specificities,
the opine dehydrogenases present a rather confusing picture. All can metabolize 2-oxobutyrate
as well as pyruvate, but they metabolize keto
acids with five or six C atoms much less, and only
a few of them can react with oxaloacetate. All
possibilities of amino acid specificity are found,
from the high specificity for glycine as the only
substrate, shown by strombine dehydrogenase
from the sponge Halichondria panicea, to the
broad specificity of the enzyme from the sea anemone Bunodosoma cavernata, which apart from
arginine and lysine metabolizes alanine, glycine
and other neutral amino acids; the latter enzyme
is classifiable as a real ODH only from the fact
that the Michaelis constants for all amino acids
other than arginine have high, non-physiological
values.
The octopine dehydrogenases can be ordered
according to their activities against OJ-amino substrates such as lysine or ornithine. First comes the
enzyme from the sea anemone Calliactis parasitica, which reacts with lysine as well as with arginine, and with lysinopine as well as with octopine; the activity with lysine among various species declines in the order Mytilus edulis > Glycimeris glycimeris > Sipunculus nudus > Sepia
brain> Sepia mantle. At the end come the ODHs
that are absolutely specific for OJ-guanidine substrates such as arginine, homo arginine or canavanine, e.g. from the mussels Arctica, Pecten, and
Anodonta [241]. A similar situation exists for the
a1anopine and strombine dehydrogenases. The
alanopine dehydrogenases of Littorina littorea
and Busycotypus canaliculatum and the strombine dehydrogenase of Halichondria panicea are
14 Glycolysis
tions and can easily switch from lactate production to lactate oxidation. This distribution of
isoenzymes of D-specific LDH allows a division of
labour between the musculature and the other tissues just like that found for the L-specific LDHs
of the vertebrates and the isoenzymes of octopine
dehydrogenase in the cephalopods [27, 70].
Isoenzymes of D-specific LDH are also found in
various gastropods but probably not as part of a
complex adapted system like that of Limulus
[183].
14.11.3 Opine Dehydrogenases
To date, five different opine dehydrogenases have
been described (Fig. 14.5). The first to be characterized, in 1959, was the opine dehydrogenase
from various molluscs and Sipunculus nudus; this
was followed in 1976 by the alanopine/strombine
dehydrogenase of the oyster Crassostrea gigas, in
1985 by the tauropine dehydrogenase of the snail
Haliotis lamellosa, and in 1987 by the ~-alanopine
dehydrogenase of the mussel Scapharca broughtonii. It is quite possible that further enzymes of
this type exist. As well as in the molluscs, octopine dehydrogenases (ODH) have since been
reported in sea anemones, nemertines, sipunculids, and brachiopods and have, in part, been characterized; in the annelids, they have as yet been
detected only in the polychaete Glycera lapidum.
The distribution of ODH amongst the molluscs is
by far the best documented. They are probably
present in all cephalopods. In the gastropods,
they are widely found in the prosobranch neogastropods as well as in several aracheo- and
mesogastropods, but not in the opisthobranchs or
pulmonates. ODHs are widely distributed in both
marine and freshwater mussels with the exceptions of the families Ostreidae and Myidae. Alanopine and strombine dehydrogenases are usually
found together in the poriferans, cnidarians,
nemertines, sipunculids, brachiopods, annelids
and mussels; in the molluscs, they are absent
from the cephalopods, gastropods, nudibranchs
(opisthobranchs) and all freshwater species
[68, 84, 140]. Tauropine dehydrogenase not only
is found in all species of the genus Haliotis but has
also recently been isolated from the stem of the
brachiopod Glottidia pyramidata [47, 69, 218]. ~Alanopine and the corresponding dehydrogenase
are only known so far in the mussel Scapharca
broughtonii [219].
All known opine dehydrogenases are monomeric proteins of about 35-40 kDa [47, 69,
70, 190, 242]. The similarities of the molecular
masses and catalytic properties make it likely that
all opine dehydrogenases are homologous,
although this awaits confirmation from sequence
data. It is already clear that there is no immunological relationship between ODH and other pyruvate dehydrogenases, and that ODH apparently
has a very high rate of evolution; antibodies
against ODH of the eight-armed cephalopod
Haplochlaena maculosa cross-react with the
ODH of all octopods but react only weakly with
the enzyme of all other cephalopods and not at all
with the enzyme of mussels and snails [70].
The reactions of the ODHs from the marine
molluscs Pecten maximus and Concholepas concholepas have been examined in detail. In the forward reaction, NADH is bound first, followed
randomly by arginine and pyruvate, whereas in
the reverse reaction first NAD+ is bound and
then octopine [28]. In the substrate specificities,
the opine dehydrogenases present a rather confusing picture. All can metabolize 2-oxobutyrate
as well as pyruvate, but they metabolize keto
acids with five or six C atoms much less, and only
a few of them can react with oxaloacetate. All
possibilities of amino acid specificity are found,
from the high specificity for glycine as the only
substrate, shown by strombine dehydrogenase
from the sponge Halichondria panicea, to the
broad specificity of the enzyme from the sea anemone Bunodosoma cavernata, which apart from
arginine and lysine metabolizes alanine, glycine
and other neutral amino acids; the latter enzyme
is classifiable as a real ODH only from the fact
that the Michaelis constants for all amino acids
other than arginine have high, non-physiological
values.
The octopine dehydrogenases can be ordered
according to their activities against OJ-amino substrates such as lysine or ornithine. First comes the
enzyme from the sea anemone Calliactis parasitica, which reacts with lysine as well as with arginine, and with lysinopine as well as with octopine; the activity with lysine among various species declines in the order Mytilus edulis > Glycimeris glycimeris > Sipunculus nudus > Sepia
brain> Sepia mantle. At the end come the ODHs
that are absolutely specific for OJ-guanidine substrates such as arginine, homo arginine or canavanine, e.g. from the mussels Arctica, Pecten, and
Anodonta [241]. A similar situation exists for the
a1anopine and strombine dehydrogenases. The
alanopine dehydrogenases of Littorina littorea
and Busycotypus canaliculatum and the strombine dehydrogenase of Halichondria panicea are