Biocatalysts from Aplysia 30.4 Glycoside Hydrolases Present in the Genus Aplysia 735
Part F | 30.4
plex structures of fucoidan, a sulphated polysaccharide
from brown algae exhibiting biological activity in mammalian systems, which is very promising for human
therapeutics[30.30].
An ˛-L-fucosidase from the liver of the marine gastropod Charonia lampas was purified to homogeneity [30.31]. Substrate-specificity studies using a number of fucosylated oligosaccharides of the
lacto-N and lacto-N-neo series and a synthetic disaccharide confirmed that the enzyme catalyzes the
hydrolysis of a broad range of fucosidic linkages.
Rhodothermus marimus ATCC 43812, a thermophilic
bacterium isolated from marine hot springs, possesses
hydrolytic activities for depolymerizing substrates such
as carob-galactomannan [30.32]. The Antarctic marine ecosystem has also been the source for the
cold-adapted ˛-galactosidase as found in Pseudoalteromonas sp. 22b [30.33]. An updated overall analysis
of the literature can be found in different articles, and
readers are referred to [30.7–9] and references cited
therein.
Different aspects should be considered for marine glycosidases. In the first place, scientific attention
has been focused on biocatalysts from marine extremophiles because of the stability and novelty of
catalytic properties that these proteins can offer and
the simplicity in which they can be expressed. Marine
glycosidases, as resulting from our analysis, are well
placed in the expanding field of glycobiology. Among
the examples, the marine ˛-galactosidase from Pseudoalteromonas [30.34], which is capable of removing
immunodeterminant sugar residues and the sialidase
from a tentatively assigned Pseudomonas used for the
preparation of GM1 from a mixture of polysialogangliosides [30.35], are two exciting cases. It is outside
the scope of this section to list each glycosyl hydrolase
isolated from sea organisms. Above, only few examples
are mentioned while in the following sections remarkable examples restricted to sea hares belonging to the
family Aplysiidae will be reported.
Aplysia is a genus of sea hares belonging to the family Aplysiidae to which Aplysia fasciata, Poiret 1798,
and Aplysia kurodai belong; these molluscs are very
common. They are herbivorous and eat a variety of red,
green, or brown algae and eelgrass [30.36]. Animals
belonging to the Aplysiidae family of sea hares are often quite large and have a rounded body shape with
long rhinophores on their heads. The Californian black
sea hare, Aplysia vaccaria, could be considered the
largest living shell-less gastropod (2075 cm, weighing well over 2 kg). They are cosmopolitan and found
in temperate and tropical seas where they inhabit shallow coastal areas or sheltered bays with vegetation. The
genus Aplysia has proved useful as a model in neurobiology for the study of electrical synapses, which
mediate the release of clouds of ink [30.37].
30.4 Glycoside Hydrolases Present in the Genus Aplysia
Various interesting results related to the presence of glycosyl hydrolases have been reported on Aplysia fasciata
and Aplysia kurodai in the last decade. Both species
have been revealed to be potent producers of a library
of glycoside hydrolases applied in the synthesis and
hydrolysis of the glycosidic bond. In this section we
analyze the results obtained in the isolation and applications of biocatalysts from A. fasciata and Aplysia
kurodai with emphasis on products, reaction conditions,
yields, and regioselectivity.
The author’s group started a general survey of
glycosidase activities present in the mollusc Aplysia
fasciata several years ago [30.38]. Three main parts
of the animal were analyzed: (i) the mantle and other
external parts, including oral tentacles, rhinophores,
eyes, foot, and parapodia; (ii) the hepatopancreas;
and (iii) other visceral mass, including the digestive, excretory, blood-vascular, and reproductive systems. Many glycosyde hydrolase activities were assayed by using chromophoric substrates of different sugars (fucose, galactose, glucose, mannose, Nacetyl glucosamine, and xylose), and interesting results were obtained. The extracts from hepatopancreas
and from visceral mass resulted rich in glycoside hydrolases; their activities were in the range found in
other marine molluscs [30.39]. By contrast, the extract of external parts did not hydrolyze any of the
substrates tested. Interestingly, the ˇ-D-galactosidase
and the ˇ-D-glucosidase enzymes from hepatopancreas and visceral mass, respectively, were present in
large amounts. An interesting ˛-mannosidase was also
noticed.
The ability of ˛-glucosidases to perform transglucosylation reactions is a relevant issue from the biotechnological point of view (in the food industry, for the
production of glycoconjugates, etc.).
Part F | 30.4
plex structures of fucoidan, a sulphated polysaccharide
from brown algae exhibiting biological activity in mammalian systems, which is very promising for human
therapeutics[30.30].
An ˛-L-fucosidase from the liver of the marine gastropod Charonia lampas was purified to homogeneity [30.31]. Substrate-specificity studies using a number of fucosylated oligosaccharides of the
lacto-N and lacto-N-neo series and a synthetic disaccharide confirmed that the enzyme catalyzes the
hydrolysis of a broad range of fucosidic linkages.
Rhodothermus marimus ATCC 43812, a thermophilic
bacterium isolated from marine hot springs, possesses
hydrolytic activities for depolymerizing substrates such
as carob-galactomannan [30.32]. The Antarctic marine ecosystem has also been the source for the
cold-adapted ˛-galactosidase as found in Pseudoalteromonas sp. 22b [30.33]. An updated overall analysis
of the literature can be found in different articles, and
readers are referred to [30.7–9] and references cited
therein.
Different aspects should be considered for marine glycosidases. In the first place, scientific attention
has been focused on biocatalysts from marine extremophiles because of the stability and novelty of
catalytic properties that these proteins can offer and
the simplicity in which they can be expressed. Marine
glycosidases, as resulting from our analysis, are well
placed in the expanding field of glycobiology. Among
the examples, the marine ˛-galactosidase from Pseudoalteromonas [30.34], which is capable of removing
immunodeterminant sugar residues and the sialidase
from a tentatively assigned Pseudomonas used for the
preparation of GM1 from a mixture of polysialogangliosides [30.35], are two exciting cases. It is outside
the scope of this section to list each glycosyl hydrolase
isolated from sea organisms. Above, only few examples
are mentioned while in the following sections remarkable examples restricted to sea hares belonging to the
family Aplysiidae will be reported.
Aplysia is a genus of sea hares belonging to the family Aplysiidae to which Aplysia fasciata, Poiret 1798,
and Aplysia kurodai belong; these molluscs are very
common. They are herbivorous and eat a variety of red,
green, or brown algae and eelgrass [30.36]. Animals
belonging to the Aplysiidae family of sea hares are often quite large and have a rounded body shape with
long rhinophores on their heads. The Californian black
sea hare, Aplysia vaccaria, could be considered the
largest living shell-less gastropod (2075 cm, weighing well over 2 kg). They are cosmopolitan and found
in temperate and tropical seas where they inhabit shallow coastal areas or sheltered bays with vegetation. The
genus Aplysia has proved useful as a model in neurobiology for the study of electrical synapses, which
mediate the release of clouds of ink [30.37].
30.4 Glycoside Hydrolases Present in the Genus Aplysia
Various interesting results related to the presence of glycosyl hydrolases have been reported on Aplysia fasciata
and Aplysia kurodai in the last decade. Both species
have been revealed to be potent producers of a library
of glycoside hydrolases applied in the synthesis and
hydrolysis of the glycosidic bond. In this section we
analyze the results obtained in the isolation and applications of biocatalysts from A. fasciata and Aplysia
kurodai with emphasis on products, reaction conditions,
yields, and regioselectivity.
The author’s group started a general survey of
glycosidase activities present in the mollusc Aplysia
fasciata several years ago [30.38]. Three main parts
of the animal were analyzed: (i) the mantle and other
external parts, including oral tentacles, rhinophores,
eyes, foot, and parapodia; (ii) the hepatopancreas;
and (iii) other visceral mass, including the digestive, excretory, blood-vascular, and reproductive systems. Many glycosyde hydrolase activities were assayed by using chromophoric substrates of different sugars (fucose, galactose, glucose, mannose, Nacetyl glucosamine, and xylose), and interesting results were obtained. The extracts from hepatopancreas
and from visceral mass resulted rich in glycoside hydrolases; their activities were in the range found in
other marine molluscs [30.39]. By contrast, the extract of external parts did not hydrolyze any of the
substrates tested. Interestingly, the ˇ-D-galactosidase
and the ˇ-D-glucosidase enzymes from hepatopancreas and visceral mass, respectively, were present in
large amounts. An interesting ˛-mannosidase was also
noticed.
The ability of ˛-glucosidases to perform transglucosylation reactions is a relevant issue from the biotechnological point of view (in the food industry, for the
production of glycoconjugates, etc.).