Effect of aerial exposure on the antioxidant status in the subantarctic stone crab Paralomis granulosa (Decapoda: Anomura)

In Tierra del Fuego (Southern South America), the stone or false king crab, Paralomis granulosa represents one of the most important crab fisheries. After capture, animals are kept in baskets and exposed to dryness for several hours, when the water flow through the gills is interrupted. As a consequence a concomitant increase of reactive oxygen species begins, triggering oxidative stress. The aim of this study was to determine oxidative stress and antioxidant enzyme activities due to air exposure in different tissues of P. granulosa. Fifty crabs (carapace length >82 mm) were captured in Beagle Channel (54 degrees 50'S, 68 degrees 20'W) during winter 2004. Five groups of 10 crabs each were exposed to dryness at 6 degrees C for 0, 3, 6, 12 or 24 h, respectively. Activity of superoxide dismutase (SOD), catalase (CAT), glutathione S transferase (GST) protein and lipid oxidation were measured in gills, muscle, hepatopancreas and haemolymph samples. Almost all analyzed tissues showed antioxidant enzymes activity, which varied with time of air exposure. The maximum enzyme activity was measured after 6 h of air exposure. Protein oxidation levels varied significantly in gills. Lipid peroxidation levels increased significantly in muscle and hepatopancreas. The critical time of air exposure probably occurs at 6 h. Thereafter animals were unable to induce the synthesis of antioxidant enzymes or proteins. This should be taken into account to minimize the stress generated by the commercial capture process.

Molecular cloning, expression of a peroxiredoxin gene in Chinese shrimp Fenneropenaeus chinensis and the antioxidant activity of its recombinant protein

Peroxiredoxin (Prx) is known to be an antioxidant protein that protects the organisms against various oxidative stresses and functions in intracellular signal transduction. A Prx gene was firstly isolated in the crustacean, Chinese shrimp Fenneropenaeus chinensis. The full-length cDNA consists of 942bp with a 594bp open reading frame, encoding 198 amino acids. The molecular mass of the deduced amino acid is 22041.17Da with an estimated pI of 5.17. Sequence comparison showed that Prx of F. chinensis shares 76%, 73% and 72% identity with that of Aedes aegypti, Branchiostoma belcheri tsingtaunese and Drosophila melanogaster, respectively. Northern blot analysis revealed the presence of Prx transcripts of F. chinensis in all tissues examined. Real-time PCR analysis indicated that the Prx showed different expression profiles in shrimp hemocytes and hepatopancreas after artificial infection with Vibrio anguillarum. In addition, a fusion protein containing Prx was produced in vitro. LC-ESI-MS analysis showed that four peptide fragments of the recombinant protein were identical to the corresponding sequence of F. chinensis Prx. And the purified recombinant proteins were shown to reduce H(2)O(2) in the presence of dithiothreitol.

Hepatopancreatic nuclease of black tiger shrimp Penaeus monodon unlikely to be involved in viral triggered apoptosis

Nucleases are phosphodiesterases that hydrolyze DNA and/or RNA. In a search for shrimp nucleases involved in apoptosis, we discovered a nuclease from hepatopancreatic cDNA of the black tiger shrimp Penaeus monodon. The full-length nuclease gene was amplified and revealed to contain 1668bp corresponding to 381 deduced amino acid residues in the mature enzyme. Sequence analysis indicated 83% nucleic acid identity and 89% amino acid identity to a nuclease from the Kuruma shrimp Penaeus japonicus (also called Marsupenaeus japonicus). Comparative analysis of sequences, conserved motifs and phylogenetic trees indicated that P. monodon nuclease (PMN) belonged to the family of DNA/RNA non-specific endonucleases (DRNSN). RT-PCR analysis using primers specific for PMN mRNA with seven different shrimp tissues revealed that expression in normal shrimp was restricted to the hepatopancreas. Semiquantitative RT-PCR analysis of PMN using hepatopancreatic mRNA from normal shrimp and from shrimp challenged with white spot syndrome virus (WSSV) indicated significant up-regulation of PMN in the hepatopancreas (P<0.05) at the early stage of viral infection but a return to baseline levels as gross signs of disease developed. At the same time, expression was always confined to the hepatopancreas and never seen in other tissues, including those reported to be prime targets for WSSV and subject to increased levels of apoptosis after infection. The results suggested that PMN is probably a digestive enzyme that is unlikely to be involved in hallmark DNA digestion associated with apoptosis.

Effects of methyl parathion on Chasmagnathus granulatus hepatopancreas: protective role of sesamol

The protective role of sesamol, an inhibitor of the mixed function oxygenase (MFO) system, against histopathological effects of methyl parathion in the hepatopancreas of the estuarine crab, Chasmagnathus granulatus, was studied. Exposure (72 h) to a sublethal dose (0.05 mg/kg/day; 10% of 72 h-LD50) of injected methyl parathion increased the percentage of damaged hepatopancreatic tubules. Presence of melanin-like deposits in the connective tissue between hepatopancreatic tubules was also observed. Antioxidant enzyme activities (catalase and glutathione S-transferase) and lipid peroxidation (LPO) levels were also increased in hepatopancreas of crabs injected with methyl parathion. Pretreatment with sesamol (0.85 mg/kg/day) significantly protected against all these effects. These findings suggest that the hepatopancreatic damages induced by methyl parathion are due to LPO of hepatopancreatocytes membranes, as a consequence of the oxidative stress generated after methyl parathion oxidative biotransformation mediated by the MFO system.

The correction of reaction rates in continuous fluorometric assays of enzymes

The kinetic data obtained from the action of a cathepsin D-like enzyme from Biomphalaria glabrata hepatopancreas (digestive gland) on MOCAc-Gly-Lys-Pro-Ile-Leu-Phe-Phe-Arg-Leu-Lys(DNp)-D-Arg-NH(2), was studied as a data prototype, generated by means of a fluorogenic substrate. An initial fluorescence, due to incomplete energy transfer, of about 8% of the values attained after complete substrate hydrolysis; a non-linear standard curve even at microM concentrations and an exponential decay of the steady state fluorescence of reaction product of the order of 10(-4) x s(-1) were the main analytical problems encountered. The standard curves for fluorescence of the substrate reaction product after 48 h of hydrolysis, and the reference compound MOCAc-Pro-Leu-Gly-NH(2), were fitted by polynomial approximation and the point derivates used as calibration factors. Time dependence of the calibration factor for the reaction product was -2.96 x 10(-4) a.u microM(-1) x s(-1) that is, in the same order of observed enzymic reaction rates. A mathematical treatment was devised for obtaining rates corrected for errors derived from the three analytical problems indicated. The method is of general application in continuous fluorometric assays, irrespective of the particular enzyme used, but of special value for substrates that present significant initial fluorescence. The reaction rates were 11% higher; as calculated by means of the calibration factor [substrate]/(final-initial fluorescence intensities), which is the prevalent procedure in the literature; leading to underestimation of K(m) and overestimation of V(max).

Scorpion digestive lipase: A member of a new invertebrate's lipase group presenting novel characteristics

Unlike classical digestive lipases, the scorpion digestive lipase (SDL) has a strong basic character. The SDL activity's optimal pH, when using tributyrin or olive oil as substrate, was 9.0. Added to that, the estimated isoelectric point of the native SDL using the electrofocusing technique, was found to be higher than 9.6. To our knowledge, this is the first report of an animal digestive lipase having such a basic character. When olive oil was used as substrate, SDL was shown to be insensitive to the presence of amphiphilic proteins such as bovine serum albumin (BSA). Furthermore, the hydrolysis was found to be specifically dependent on the presence of Ca(2+) ions, since no significant SDL activity was detected in the presence of ions chelator such as EDTA. Nevertheless, the SDL does not require Ca(2+) to trigger the hydrolysis of tributyrin emulsion. Interestingly Zn(2+) and Cu(2+) ions act as strong inhibitors of SDL activity when using tributyrin as substrate. An internal chymotryptic cleavage of SDL generated two fragments of 28 and 25 kDa having the same N-terminal sequence. This sequence of 19 residues does not share any homology with known animal and microbial lipases. Polyclonal antibodies directed against SDL (pAbs anti-SDL) failed to recognise ostrich pancreatic and dog gastric lipases (OPL and rDGL). Moreover, both pAbs anti-OPL and anti-rDGL failed to immunoreact with SDL. These immunological as well as distinct biochemical properties strengthen the idea that SDL appears to belong to a new invertebrate's lipase group.

[Properties of chitinolytic enzymes from the hepatopancreas of the red king crab (Paralithodes camtschaticus)]

Our study confirms the presence of chitinolytic, chitosanolytic, and deacetylase activities in the hepatopancreas of the red king crab, related to the specific diet of this species. The maximum rate of chitin/chitosan hydrolysis by an enzyme preparation from crab hepatopancreas occurs at 36.5-37.0 degrees C. Two pH optimums have been found for the enzymatic reaction under mildly alkaline and acidic conditions for both exo- and endochitinase activities. The enzyme preparation is most affine to partly deacetylated chitin with an acetylation degree within 40-50%.

Esterase activities and lipid peroxidation levels in offshore commercial species of the NW Mediterranean Sea

There is a lack of information on monitoring neurotoxicity in offshore commercial species. To help fill this gap, we sampled hake (Merluccius merluccius) and Norway lobster (Nephrops norvegicus) in fishing grounds off the coast of l'Ametlla de Mar (NW Mediterranean) in June 2005 at a depth of 100 m and 400 m. Additionally, at 400 m depth, two other fish species, Micromesistius poutassou and Phycis blennoides were included. Neurotoxicity markers such as Colinesterases (ChEs), namely acethyl- (AChE), butyryl- (BChE), propionyl- (PrChE) and carboxilesterase (CbE) were measured in muscle. Lipid peroxidation (LP), a marker of oxidative damage, was also included. The results are discussed in relation to the animal's sex, size and fishing depth. A comparison of esterases and LP levels between muscle and liver of hake and between muscle and hepatopancreas of Norway Lobster was made. AChE was dominant in muscle and CbE in hepatopancreas. No differences between fish species were seen for AChE. However, N. norvegicus, presented lower levels of ChEs and LP. A size-dependence in ChEs was seen for M. merluccius, with larger animals showing significantly lower activities (p<0.05). Sex-dependence was seen in N. norvegicus for most esterases, except AChE, with males displaying higher activities (p<0.05). A sampling-depth effect was also seen in the crustacea, with animals from 100 m generally presenting lower esterase activities and higher LP levels.

Food digestion by cathepsin L and digestion-related rapid cell differentiation in shrimp hepatopancreas

Cathepsin L (CatL) has been readily localized in the large vacuole and in the apical complex of the digestive B-cell of the shrimp hepatopancreas. Immunogold technique revealed the occurrence of CatL in zymogen granule, digestive body and digestive vacuole of the B-cell in the hepatopancreas of Metapenaeus ensis. Coalescences of zymogen granule with sub-apical vacuole, and of two small digestive bodies were observed. This progressive coalescence of CatL vesicles is direct evidence of involvement of CatL in intracellular digestion. Released CatL vesicles and free CatL were found in the lumen of hepatopancreatic tubule. CatL mRNA existed in F-cell, but not in the mature B-cell. This finding supports the previous suggestion that F-cell is the precursor of B-cell. F-cell is a transient form. Transition from F-cell to B-cell is fast. We define F-cell as the transcribing cell, F/B-cell as the enzyme-synthesizing cell and B-cell as the enzyme-secreting cell. For the first time, we suggest that R-cell is the replacing cell for the leaving B-cell. CatL degrades nutrient intracellularly and extracellularly. The most interesting finding is that CatL is transcribed in one type of cell, and the very cell evolves quickly to a morphologically different cell where the enzyme functions.

Cloning and characterisation of mitochondrial manganese superoxide dismutase (mtMnSOD) from the giant freshwater prawn Macrobrachium rosenbergii

A cDNA encoding a mitochondrial manganese superoxide dismutase (mtMnSOD) was cloned from the hepatopancreas of giant freshwater prawn Macrobrachium rosenbergii using reverse transcription polymerase chain reaction (RT-PCR) by degenerate primers. Both 3'- and 5'-regions were isolated by rapid amplification of cDNA end (RACE) PCR method. Analysis of nucleotide sequence revealed that the mtMnSOD full-length cDNA consists of 1202bp containing an open reading frame of 654bp, which encodes a protein consisting of 218 amino acids including a signal peptide of 16 amino acid residues. The calculated molecular mass of the mature proteins (202 amino acids) is 24kDa with an estimated pI of 7.12. Two putative N-glycosylation sites, NXT and NXS were observed in the mtMnSOD. Manganese superoxide dismutase signatures from 180 to 187 (DVWEHAYY), and four conserved amino acids responsible for binding manganese were observed (H48, H96, D180 and H184). Sequence comparison showed that the mtMnSOD deduced amino acid sequence of Macrobrachium rosenbergii has similarity of 88%, 78%, 56%, 54% and 46% to that of blue crab Callinectes sapidus, crucifix crab Charybdis feriatus, brown shrimp Farfantepenaeus aztecus, European lobster Palinurus vulgaris, and grass shrimp Palaemontes pugio, respectively, and has similarity of 45%, 44%, 43%, 26% and 25% to cytMnSOD (cytosolic MnSOD) deduced amino acid sequence of blue crab C. sapidus, prawn M. rosenbergii, tiger shrimp Penaeus monodon, grass shrimp P. pugio and brown shrimp F. aztecus, respectively. Quantitative real-time RT-PCR analysis showed that levels of mtMn-SOD transcripts in hepatopancreas and haemocytes were not significantly different between the M. rosenbergii injected with Lactococcus garvieae, and that injected with saline after 3h to 24h.

Biochemical and physiological responses after exposure to microcystins in the crab Chasmagnathus granulatus (Decapoda, Brachyura)

Microcystins are usually the predominant cyanotoxins present in both drinking and recreational waters after cyanobacterial blooms. Their classic toxic effect is hepatotoxicity through inhibition of serine/threonine phosphatases. However, recent studies also reported oxidative stress generation and disruption of ion regulation in aquatic organisms after microcystins exposure. In the present study, aqueous extracts of Microcystis aeruginosa were administered to the estuarine crab Chasmagnathus granulatus (Decapoda, Brachyura) by gavage in variable doses (from 34 to 860 microg kg(-1)) and exposure times (6, 12, and 72 h). A control group was exposed to saline solution. Analyzed variables included oxygen consumption, lipid peroxidation (LPO), enzyme activities (glutathione S-transferases or GST; alanine aminotransferase or ALT; aspartate aminotransferase or AST; and lactate dehydrogenase or LDH), glycogen, and microcystins content. Oxygen consumption increased in organisms exposed for 12h to 860 microg kg(-1) of microcystins and a similar result was observed after 72 h at doses equal to or higher than 34 microg kg(-1). LPO levels increased in doses equal to or higher than 34 microg kg(-1) after 72 h. GST and LDH activities increased after 12 h (at a dose of 860 microg kg(-1)), but ALT and AST activities remained unaltered in all experimental conditions. Glycogen content decreased after 72 h exposure at doses equal to or higher than 172 microg kg(-1). After 12h of exposure to 860 microg kg(-1) of microcystins, the concentration found in the hepatopancreas of C. granulatus was 13.17+/-0.56 microg kg(-1). In crabs exposed to doses higher than 172 microg kg(-1) during 72 h this value raised to 32.14+/-4.12 microg kg(-1). The obtained results indicated that microcystins exposure led the tissue to an oxidative stress condition (high LPO levels), at least in part favored by the augment of oxygen consumption, altering the glycogen metabolism. GST responses were only observed in the short-term experiment (12 h) and no effect on classical markers of vertebrate liver damage (ALT and AST) was observed. Although the hepatopancreas from C. granulatus accumulated a relatively low concentration of toxins, it was enough to induce physiological and biochemical disturbances.

Toxicity of hexachlorobenzene and its transference from microalgae (Chlorella kessleri) to crabs (Chasmagnathus granulatus)

The aim of this work was to study the transference of hexachlorobenzene from a green alga (Chlorella kessleri) to an estuary crab (Chasmagnathus granulatus), and to analyze the toxic effects that the xenobiotic has on the latter. The effect of hexachlorobenzene uptake was evaluated measuring oxidative stress, Uroporphyrinogen decarboxylase activity and morphometric parameter alteration, and also performing a histological analysis of crab hepatopancreas. Results demonstrated that hexachlorobenzene enters the alga, is accumulated in it, and then transferred into the crab, causing a decrease in Uroporphyrinogen decarboxylase activity in both organisms. The high malondialdehyde levels detected in crab hepatopancreas after the toxic treatment suggested the existence of hexachlorobenzene-induced lipid peroxidation. Antioxidant defenses such as superoxide dismutase activity and reduced glutathione content fell below normal values on the fourth week of treatment. At the same time, the hepatosomatic index, used as a morphometric parameter, reduced 20% with respect to the control. The histological analysis revealed epithelium disorganization in hepatopancreas tubules, confirming the existence of structural damage caused by hexachlorobenzene.

Immunocytochemical localization of scorpion digestive lipase

The scorpion hepatopancreas consists of digestive diverticula and interstitial tissue. A digestive diverticulum is composed of two differentiated cell types: the secretory zymogene-like cells and the digestive cells which are the most abundant. The scorpion digestive lipase (SDL) has been previously purified from scorpion hepatopancreas, but its cellular localization has not yet been established. Polyclonal antibodies specific to SDL were prepared and used in immunofluorescence and immunogold techniques to determine the cellular location of SDL. Our results clearly established that SDL was detected intracellularly in specific vesicles tentatively named (SDL+) granules of the digestive cells. No immunolabelling was observed in secretory zymogene-like cells. This immunocytolocalization indicates that lipid digestion might occur in specific granules inside the digestive cells, as suggested by previous studies on the scorpion digestive process.

Molecular cloning and characterisation of copper/zinc superoxide dismutase (Cu,Zn-SOD) from the giant freshwater prawn Macrobrachium rosenbergii

A copper/zinc superoxide dismutase (Cu,Zn-SOD) cDNA was cloned from the hepatopancreas of giant freshwater prawn Macrobrachium rosenbergii using reverse transcription-polymerase chain reaction (RT-PCR) by degenerate primers. Both 3'- and 5'-regions were isolated by the rapid amplification of cDNA ends method. Analysis of nucleotide sequence revealed that the Cu,Zn-SOD cDNA clone consists of 845 bp with an open reading frame of 603 bp encoding a protein of 201 amino acids with a 22 amino acid signal peptide. The calculated molecular mass of the mature proteins (179 amino acids) is 21 kDa with an estimated pI of 4.75. Two putative N-glycosylation sites, NXT and NXS, were observed in the Cu,Zn-SOD. Four conserved amino acids responsible for binding copper (H86, H89, H106 and H163) and four conserved amino acids responsible for binding zinc (H106, H114, H123 and D126) were observed. Sequence comparison showed that the Cu,Zn-SOD deduced amino acid sequence of M. rosenbergii has similarity of 60% and 64% to that of freshwater crayfish Pacifastacus leniusculus ecCu,Zn-SOD and blue crab Callinectes sapidus ecCu,Zn-SOD, respectively. Quantitative real-time RT-PCR analysis showed that Cu,Zn-SOD transcripts in haemocytes of M. rosenbergii increased 3h and 6h after injection of Lactococcus garvieae, whereas Cu,Zn-SOD transcripts decreased in the hepatopancreas 3h after L. garvieae injection.

Subcellular/tissue distribution and responses to oil exposure of the cytochrome P450-dependent monooxygenase system and glutathione S-transferase in freshwater prawns (Macrobrachium malcolmsonii, M. lamarrei lamarrei)

Subcellular fractions (mitochondrial, cytosolic and microsomal) prepared from the tissues (hepatopancreas, muscle and gill) of freshwater prawns Macrobrachium malcolmsonii and Macrobrachium lamarrei lamarrei were scrutinized to investigate the presence of mixed function oxygenase (MFO) and conjugating enzymes (glutathione-S-transferase, GST). Cytochrome P450 (CYP) and other components (cytochrome b(5); NADPH-cytochrome c (CYP) reductase and NADH-cytochrome c-reductase activities) of the MFO system were predominantly present in the hepatic microsomal fraction of M. malcolmsonii and M. lamarrei lamarrei. The results are in agreement with the notion that monooxygenase system is mainly membrane bound in the endoplasmic reticulum, and that the hepatopancreas is the major metabolic tissue for production of biotransformation enzymes in crustaceans. Further, the prawns were exposed to two sublethal (0.9 ppt (parts per thousand) and 2.3 ppt) concentrations of oil effluent. At the end of 30th day, hydrocarbons and detoxifying enzymes were analysed in the hepatopancreas. The accumulations of hydrocarbon in the tissues gradually increased when exposed to sublethal concentrations of oil effluent and were associated with significantly enhanced levels of cytochrome P450 (180.6+/-6.34 pmol mg(-1) protein (P<0.05 versus control, 136.5+/-7.1 pmol mg(-1) protein) for 2.3 ppt and 305.6+/-8.5 pmol mg(-1) protein (P<0.001 versus control, 132.3+/-6.8 pmol mg(-1) protein] for 0.9 ppt of oil exposed M. malcolmsonii; 150+/-6.5 pmol mg(-1 )protein (P<0.01 versus control, 84.6+/-5.2 pmol mg(-1) protein) for 2.3 ppt and 175+/-5.5 pmol mg(-1) protein (P<0.01 versus control, 87.6+/-5.4 pmol mg(-1) protein) for 0.9 ppt of oil exposed M. lamarrei lamarrei), NADPH cytochrome c-reductase activity (14.7+/-0.6 nmol min(-1 )mg(-1) protein (P<0.05 versus control, 6.8+/-0.55 nmol min(-1 )mg(-1) protein) for 2.3 ppt and 12.1+/-0.45 nmol min(-1 )mg(-1) protein (P<0.01 versus control, 6.9+/-0.42 nmol min(-1 )mg(-1) protein) for 0.9 ppt of oil exposed M. malcolmsonii; 12.5+/-0.31 nmol min(-1 )mg(-1) protein (P<0.001 versus control, 4.6+/-0.45 nmol min(-1 )mg(-1) protein) for 2.3 ppt and 9.6+/-0.32 nmol min(-1 )mg(-1) protein (P<0.01 versus control, 4.9+/-0.41 nmol min(-1 )mg(-1) protein) for 0.9 ppt of oil exposed M. lamarrei lamarrei) and cytochrome b(5 )(124.8+/-3.73 pmol mg(-1) protein (P<0.01 versus control, 76.8+/-4.2 pmol mg(-1) protein) for 2.3 ppt and 115.3+/-3.86 pmol mg(-1) protein (P<0.01 versus control, 76.4+/-4.25 pmol mg(-1 )protein) for 0.9 ppt of oil exposed M. malcolmsonii and 110+/-3.11 pmol mg(-1) protein (P<0.01 versus control, 63.7+/-3.24 pmol mg(-1 )protein) for 2.3 ppt and 95.3+/-2.63 pmol mg(-1) protein (P<0.01 versus control, 61.4+/-2.82 pmol mg(-1) protein) for 0.9 ppt of oil exposed M. lamarrei lamarrei). The enhanced levels of biotransformation enzymes in oil-exposed prawns demonstrate a well-established detoxifying mechanism in crustaceans, and the response offers the possibility of use as a biomarker for the early detection of oil pollution.

Suppression of Na+/K+-ATPase activity during estivation in the land snail Otala lactea

Entry into the hypometabolic state of estivation requires a coordinated suppression of the rate of cellular ATP turnover, including both ATP-generating and ATP-consuming reactions. As one of the largest consumers of cellular ATP, the plasma membrane Na+/K+-ATPase is a potentially key target for regulation during estivation. Na+/K+-ATPase was investigated in foot muscle and hepatopancreas of the land snail Otala lactea, comparing active and estivating states. In both tissues enzyme properties changed significantly during estivation: maximal activity was reduced by about one-third, affinity for Mg.ATP was reduced (Km was 40% higher), and activation energy (derived from Arrhenius plots) was increased by approximately 45%. Foot muscle Na+/K+-ATPase from estivated snails also showed an 80% increase in Km Na+ and a 60% increase in Ka Mg2+ as compared with active snails, whereas hepatopancreas Na+/K+-ATPase showed a 70% increase in I50 K+ during estivation. Western blotting with antibodies recognizing the alpha subunit of Na+/K+-ATPase showed no change in the amount of enzyme protein during estivation. Instead, the estivation-responsive change in Na+/K+-ATPase activity was linked to posttranslational modification. In vitro incubations manipulating endogenous kinase and phosphatase activities indicated that Na+/K+-ATPase from estivating snails was a high phosphate, low activity form, whereas dephosphorylation returned the enzyme to a high activity state characteristic of active snails. Treatment with protein kinases A, C or G could all mediate changes in enzyme properties in vitro that mimicked the effect of estivation, whereas treatments with protein phosphatase 1 or 2A had the opposite effect. Reversible phosphorylation control of Na+/K+-ATPase can provide the means of coordinating ATP use by this ion pump with the rates of ATP generation by catabolic pathways in estivating snails.

Scorpion digestive lipase: kinetic study using monomolecular film technique

Using the classical emulsified system and the monomolecular film technique, we compared the interfacial properties of the scorpion digestive lipase (SDL) with those of higher animals'. In the absence of bile slats, SDL does not hydrolyse efficiently pure tributyrin, as well as dicaprin films maintained at low surface pressure. The preincubation of bile salts with tributyrin seems to be a better substrate for SDL than the pure tributyrin. A kinetic study on the surface pressure dependency, stereospecificity and regioselectivity of SDL was performed using monomolecular films of either three dicaprin isomers or three pairs of didecanoyl-deoxyamino-O-methyl glycerol enantiomers (DDG) containing a single hydrolysable decanoyl ester bond. With all diacylglycerol isomers, SDL has a surface pressure threshold of about 15 m Nm(-1), below which enzymatic activity is undetectable. SDL seems to prefer vicinal ester groups of the diacylglycerol isomers, with preference for sn-1 position at both 15 and 23 m Nm(-1). Furthermore, the maximum SDL activity is measured with DDG having a primary ester bond (1,3DDG, SII). This shows that SDL has a preference for the sn-1 position of this diacylglycerol analogue. Moreover, this was in line with the fact that SDL is inactive on sn-2 position of both DDG isomers and a triacylglycerol. With diacylglycerol analogue isomers, SDL shows a preference for distal isomers contrary to what has been observed with diacylglycerol isomers. SDL interacts with egg-phosphatidyl choline (egg-PC) monomolecular films. The critical surface pressure value (13 m Nm(-1)) is comparable to those of pancreatic lipases.

Molecular cloning and characterisation of cytosolic manganese superoxide dismutase (cytMn-SOD) from the giant freshwater prawn Macrobrachium rosenbergii

A cytosolic manganese superoxide dismutase (cytMn-SOD) cDNA was cloned from the hepatopancreas of giant freshwater prawn Macrobrachium rosenbergii using reverse transcription polymerase chain reaction (RT-PCR) by degenerate primers. Both 3'- and 5'-regions were isolated by rapid amplification of cDNA end RACE method. Analysis of nucleotide sequence revealed that the cytMn-SOD cDNA clone consists of 1339 bp with an open reading frame of 858 bp encoding a protein of 286 amino acids. The calculated molecular mass of the mature proteins (286 amino acids) is 31 kDa with an estimated pI of 5.52. Two putative N-glycosylation sites, NXT and NXS were observed in the cytMn-SOD. Four conserved amino acids responsible for binding manganese were observed (H110, H158, D243 and H247). Sequence comparison showed that the cytMn-SOD deduced amino acid sequence of M. rosenbergii has an overall similarity of 77% and 54% to that of blue crab Callinectes sapidus and tiger shrimp Penaeus monodon, respectively. Quantitative real-time RT-PCR analysis showed that cytMn-SOD transcript in hepatopancreas of M. rosenbergii decreased 3h after Lactococcus garvieae injection, but no significant change in cytMn-SOD transcript was observed in the haemocytes 3-24 h after L. garvieae injection.

Activities of membrane bound phosphatases, transaminases and mitochondrial enzymes in white spot syndrome virus infected tissues of Fenneropenaeus indicus

Disease caused by viruses, especially white spot syndrome virus (WSSV), present the greatest challenge to shrimp aquaculture worldwide. Massive tissue disintegration occurs in WSSV-infected ectodermal and mesodermal tissues of penaeid shrimp. The activities of membrane bound phosphatases (Na(+)K(+)ATPase, Ca(2+)ATPase, Mg(2+)ATPase and Total ATPase), transaminases (alanine transaminase (ALT) and aspartate transaminase (AST)) and mitochondrial enzymes (isocitrate dehydrogenase (ICDH), succinate dehydrogenase (SDH), malate dehydrogenase (MDH), alpha-ketoglutarate dehydrogenase (KGDH), NADH dehydrogenase, cytochrome C oxidase) in WSSV-infected tissues (hemolymph, hepatopancreas, gills and muscle) of Fenneropenaeus indicus were determined at intervals after WSSV infection (0, 24, 48, 72 and after 72 h (moribund)). The activities of phosphatases, transaminases and mitochondrial enzymes in healthy as compared with WSSV-infected hemolymph, hepatopancreas, gills and muscle showed marked divergence throughout the course of infection. WSSV infected hemolymph, hepatopancreas, gills and muscle exhibited significantly reduced activity of membrane bound phosphatases compared with the uninfected animals. Inactivation of these enzymes may occur due to increased production of free radicals, that cause conformational change by oxidation of 'SH' groups present at the active site. Significantly marked elevation in the activities of transaminases (ALT and AST) was observed in WSSV-infected hemolymph, hepatopancreas, gills and muscle compared to the uninfected tissues. This may be due to leakage of these enzymes from the damaged tissues. The activities of mitochondrial enzymes in WSSV-infected tissues were significantly decreased compared to the activities in uninfected animals. WSSV-infected animals showed reduced feeding that may have led to decreased oxidation of glucose via the TCA cycle. Excessive production of free radicals in WSSV-infected animals may have affected aerobic oxidation leading to lower production of ATP. It is concluded that membrane dynamics play a major role in the pathogenesis of WSSV infection.

Analysis of signal transduction pathways during anoxia exposure in a marine snail: A role for p38 MAP kinase and downstream signaling cascades

The responses of members of the three main MAPK families (ERK, JNK/SAPK, p38 MAPK), as well as selected peripheral pathways, were examined in hepatopancreas of the marine periwinkle, Littorina littorea, to determine if anoxia exposure influenced the total protein content or the phosphorylation status of any key components. The content of active phospho-p38 MAPK was 2-fold higher in hepatopancreas from anoxic snails relative to controls. A 1.7-fold increase in the amount of phospho-Hsp27 and a 1.3-fold increase in phospho-CREB correlated well with the changes in p38 MAPK phosphorylation. Activation of these factors via p38 MAPK may be vital to the reorganization of metabolic responses to anoxia in hepatopancreas. No changes in components of the JNK/SAPK and ERK pathways occurred and transcription factors involved in lipid metabolism did not appear to be affected by anoxia. The present analysis of a variety of signaling pathways has implicated the p38 MAPK pathway as a key anoxia-responsive signal transduction pathway in L. littorea.

Fluctuations of biochemical constituents and marker enzymes as a consequence of naphthalene toxicity in the edible estuarine crab Scylla serrata

The sublethal effects of naphthalene on protein, deoxyribonucleic acid (DNA), ribonucleic acid (RNA), carbohydrates, lipids, and certain marker enzymes such as phosphatases, transaminases, and lactate dehydrogenase were studied in hepatopancreas, hemolymph, and ovary in the edible crab Scylla serrata. The results revealed that there was overall decrease in total protein, total DNA, total RNA, free sugar, glycogen, protein-bound sugars, neutral lipid, glycolipid, and phospholipid in the test samples compared to control. Similarly all the marker enzymes (acid phosphatase, alkaline phosphatase, aspartate transaminase, alanine transaminase, and lactate dehydrogenase) were decreased in hepatopancreas and ovary. On the other hand, in hemolymph, the activities of marker enzymes were increased. The results were tested statistically and interpreted accordingly.

[Effects of heavy metal ions on SOD activity of Litopenaeus vannamei hepatopancreas, gill and blood]

This paper studied the effects of Cu2+ , Zn2+ and Cd2+ on the superoxide dismutase (SOD) activity of Litopenaeus vannamnei hepatopancreas, gill and blood. The results showed that the SOD activity changed significantly with prolonged exposure of these ions (P < 0.05). The SOD activity of all test objectives changed with a single peak under the exposure of 0.1 - 1 mg Cu2+ x L(-1), that of hepatopancreas and of hepatopancreas and gills was inhibited obviously under 10 mg Zn2+ x L(-1) and 0.5 mg Cd2+ x L(-1), respectively, while 0.25 mg Cd2+ x L(-1) had no significant effect on that of gill. The SOD activity of hepatopancreas, gill and blood all increased first and then decreased under the prolonged exposure of < 10 mg Zn2+ x L(-1) and < 0.25 mg Cd2+ x L(-1). There was an obvious dose-time response relationship between test metal ions and SOD activity. The SOD activity was decreased in order of hepatopancreas > gill > blood, while the toxicity of test metal ions was in order of Cd2+ > Cu2+ > Zn2+.

Copper-induced changes in tissue enzyme activity in a freshwater mussel

Changes in enzyme activity levels are of great diagnostic value. Lysosomal membrane is often the target of injury by xenobiotics, resulting in destabilization. Variations in the activity of acid phosphatase (ACP) a marker enzyme, in gills and hepatopancreas of the freshwater mussel Lamellidens corrianus (Lea) exposed to different concentrations of copper for 24, 120, and 168 h are discussed. The aim was to determine if the metal caused any variation in enzyme activity in the two tissues studied and, if so, whether the length of exposure had any influence on enzyme activity. ACP activity was determined as described in Sigma Technical Bulletin No. 104 and expressed as micromoles of p-nitrophenol liberated per milligram of protein per hour. Both concentration of the metal and length of exposure were found to influence enzyme activity. Higher concentrations of metals are assumed to induce stress proteins like metallothioneins.

Isolation, purification and characterization of collagenase from hepatopancreas of the land snail Achatina fulica

Collagenase (matrix metalloproteinase-1, EC:3.4.24.7) was isolated from the hepatopancreas of Achatina fulica and characterized for its enzymatic activity and immunological properties. Procollagenase was isolated using ammonium sulphate precipitation and gel filtration, followed by purification by reverse-phase high performance liquid chromatography in the presence of trifluoroacetic acid and by dialysis in neutral buffer. In the presence of SDS and beta-mercaptoethanol, the procollagenase resolved into two subunits with molecular masses of 63 and 28 kDa, respectively. The 63 kDa fragment retained its ability to bind and degrade gelatin, but the 28 kDa was inactive. Analysis by 2D gel electrophoresis revealed that the 63 kDa fragment was basic (pIs 7.6, 7.8 and 8.15), while the 28 kDa fragment was acidic (pI 4.7 and 5.1). Western blot analysis confirmed the identity of collagenase, as only matrix metalloproteinase-1 rabbit antibodies against human matrix metalloproteinase-1 (N-terminal region) recognized both the isolated procollagenase and the 63 kDa fragment.

Catalytic and structural characteristics of carp hepatopancreas D-amino acid oxidase expressed in Escherichia coli

D-amino acid oxidase of carp (Cyprinus carpio) hepatopancreas was overexpressed in Escherichia coli cells and purified to homogeneity for the first time in animal tissues other than pig kidney. The purified preparation had a specific activity of 293 units mg(-1) protein toward D-alanine as a substrate. It showed the highest activity toward D-alanine with a low Km of 0.23 mM and a high kcat of 190 s(-1) compared to 10 s(-1) of the pig kidney enzyme. Nonpolar and polar uncharged D-amino acids were preferable substrates to negatively or positively charged amino acids. The enzyme exhibited better thermal and pH stabilities than several yeast counterparts or the pig kidney enzyme. Secondary structure topology consisted of 11 alpha-helices and 17 beta-strands that differed slightly from pig kidney and Rhodotorula gracilis enzymes. A three-dimensional model of the carp enzyme constructed from a deduced amino acid sequence resembled that of pig kidney D-amino acid oxidase but with a shorter active site loop and a longer C-terminal loop. Judging from these characteristics, carp D-amino acid oxidase is close to the pig kidney enzyme structurally, but analogous to the R. gracilis enzyme enzymatically in turnover rate and pH and temperature stabilities.

Preliminary studies of biochemical changes (ethoxycoumarin O-deethylase activities and vitellogenin induction) in two species of shrimp (Farfantepenaeus duorarum and Litopenaeus setiferus) from the Gulf of Mexico

Several investigations have demonstrated that the increase in chemicals in the environment may have caused effects on aquatic life and wildlife. The impact from oil production activities on the benthic community structure and shrimp (Farfantepenaeus duorarum and Litopenaeus setiferus) biochemical markers were studied in the Gulf of Mexico, which is heavily contaminated by polycyclic aromatic hydrocarbons and heavy metals. Shrimp were collected from a control area and from an area close to oil production platforms during October and November 2002. There was no spatial difference in exposure and response probably because shrimp migrate, as results did not show significant differences in cytochrome P4501A (as measured by ethoxycoumarin O-deethylase (ECOD) metabolism) between the two sites. In October, shrimp ECOD activities were higher and statistically different from those measured in the samples taken in November. As for ECOD activities, with the concentration of vitellogenin as another biomarker, there were no differences between the shrimp collected from the control area and the shrimp collected on the oil production platforms. In this case the concentrations were higher in shrimp collected in November vs. shrimp collected in October. However, there are significant correlations between contaminants and responses (biomarkers), indicating an effect of pollution. One of the most important considerations brought up by this kind of study is that, although the majority of groups studying the effects of endocrine disruption have focused almost exclusively on human health or vertebrate wildlife-related issues, it is necessary to increase research focused on understanding the function of hormones in invertebrate species exposed in the field to different kinds of pollutants.

Molecular cloning and characterization of alpha-class glutathione S-transferase genes from the hepatopancreas of red sea bream, Pagrus major

Two distinct cDNAs corresponding to GSTA1 and GSTA2 genes encoding glutathione S-transferases (GSTs) from the hepatopancreas of red sea bream, Pagrus major were cloned and sequenced. A comparison of the nucleotide sequences of GSTA1 and GSTA2 revealed 98% identity and their derived amino acid sequences had 96% similarity. Both genes could be classified as alpha-class GSTs on the basis of their amino acid sequence identity with other species. Genomic DNA cloning showed that both GSTA1 and GSTA2 genes consisted of six exons and five introns. In a comparison of genomic DNAs, the structures of GSTA1 and GSTA2 differed. In addition, Southern-blot analysis indicated that at least two kinds of alpha-class GSTs existed in the P. major genome. In order to biochemically characterize the recombinant enzymes (pmGSTA1-1 and pmGSTA2-2), both clones were highly expressed in Escherichia coli. The purified pmGSTA1-1 and pmGSTA2-2 exhibited glutathione conjugating activity toward 1-chloro-2,4-dinitrobenzene and glutathione peroxidase activity toward cumene hydroperoxide, while neither pmGSTs show detectable activity toward 1,2-dichloro-4-nitrobenzene, ethacrynic acid, 4-hydroxynonenal, or p-nitrobenzyl chloride. Despite their high level of amino acid sequence identity, the pmGSTs had quite different enzyme-kinetic parameters.

Purification and catalytic properties of glutathione transferase from the hepatopancreas of crayfishmacrobrachium vollenhovenii (herklots)

Glutathione transferase from the hepatopancreas of fresh water crayfish Macrobrachium vollenhovenii was purified to apparent homogeneity by ion-exchange chromatography on DEAE-cellulose and by gel filtration on Sephadex G-100. The enzyme appeared to be a homodimer with molecular weight (Mr) of 46.0 +/- 1.4 kDa and a subunit Mr of 24.1 +/- 0.35 kDa. Chromatofocusing of the apparently pure enzyme revealed microheterogeneity and resolved it into two isozymic peaks, which were eluted at pH 8.36 and 8.22 respectively. Inhibition studies showed that the I50 value for cibacron blue, S-hexylglutathione, hematin, and N-ethylmaleimide (NEM) were 0.01 microM, 340 microM, 5 microM and 33 mM respectively. Out of the several substrates tested, only 1-chloro-2,4-dinitrobenzene (CDNB) and 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole could be conjugated with glutathione. Chemical modification studies with DTNB revealed that two sulphydryl groups per dimer were essential to the activity of the enzymes. On the basis of structural and catalytic characteristics, M. vollenhovenii GST seems close, tentatively, to the omega and zeta classes of GST. Initial-velocity studies of the enzyme are consistent with a steady-state random kinetic mechanism. Denaturation and renaturation studies with guanidine HCl (Gdn-HCl) revealed that though low Gdn-HCl concentrations (less than 0.5 M) denatured the enzyme, the enzyme was able to renature completely (100%). At higher concentration of the denaturant (0.5-4 M), refolding studies indicated that complete renaturation was not achieved. The extent of renaturation was however a function of protein concentration. Our results are consistent with a three-state unfolding process.

Factorial effects of salinity, dietary carbohydrate and moult cycle on digestive carbohydrases and hexokinases in Litopenaeus vannamei (Boone, 1931)

Litopenaeus vannamei were reared in close cycle over seven generations and tested for their capacity to digest starch and to metabolise glucose at different stages of the moulting cycle. After acclimation with 42.3% of carbohydrates (HCBH) or 2.3% carbohydrates (LCBH) diets and at high salinity (40 g kg(-1)) or low salinity (15 g kg(-1)), shrimp were sampled and hepatopancreas (HP) were stored. Total soluble protein in HP was affected by the interaction between salinity and moult stages (p<0.05). Specific activity of alpha-amylase ranged from 44 to 241 U mg protein(-1) and a significant interaction between salinity and moult stages was observed (p<0.05), resulting in highest values at stage C for low salinity (mean value 196.4 U mg protein(-1)), and at D0 in high salinity (mean value 175.7 U mg protein(-1)). Specific activity of alpha-glucosidase ranged between 0.09 and 0.63 U mg protein(-1), an interaction between dietary CBH and salinity was observed for the alpha-glucosidase (p<0.05) and highest mean value was found in low salinity-LCBH diet treatment (0.329 U mg protein(-1)). Hexokinase specific activity (range 9-113 mU mg protein(-1)) showed no significant differences when measured at 5 mM glucose (p>0.05). Total hexokinase specific activity (range 17-215 mU mg protein(-1)) showed a significant interaction between dietary CBH and salinity (p<0.05) with highest value (mean value 78.5 mU mg protein(-1)) found in HCBH-high salinity treatment, whereas in the other treatments the activity was not significantly different (mean value 35.93 mU mg protein(-1)). A synergistic effect of dietary CBH, salinity and moult stages over hexokinase IV-like specific activity was also observed (p<0.05). As result of this interaction, the highest value (135.5+/-81 mU mg protein(-1)) was observed in HCBH, high salinity at D0 moult stage. Digestive enzymes activity is enhanced in the presence of high starch diet (HCBH) and hexokinase can be induced at certain moulting stages under the influence of blood glucose level. Perspectives are opened to add more carbohydrates in a growing diet, exemplifying the potential approach for less-polluting feed.

Common carp metallothionein-1 gene: cDNA cloning, gene structure and expression studies

Metallothionein-1 (MT-1) cDNA clones were isolated from a common carp (Cyprinus carpio) uninduced hepatopancreas cDNA library. Northern blot assay using the common carp (cc) MT-1 cDNA as a probe showed high fold induction of ccMT mRNA levels in the intestine and kidney following exposure to Cd2+ and Zn2+. Using polymerase chain reaction (PCR), primers designed from the cDNA sequences allowed the isolation of ccMT-1 gene fragments including the 5'-flanking region. The 600 bp 5'-flanking region of ccMT-1 gene carries four putative metal regulatory regions, one AP1, two SP1, one c-Jun site, and a TATA box. The 5'-flanking region of the ccMT-1 gene obtained was a functional promoter responding to the administration of various metal ions as well as hydrogen peroxide (H2O2) and lipopolysaccharide (LPS). When tested in primary cultures of cc hepatocytes, Zn2+ had the highest fold (20 times) induction of the 600 bp cloned ccMT-1 gene promoter, followed by Cu2+, Hg2+, Ni2+ and Pb2+ (4-5-fold inductions); H2O2 and LPS had a 6-7-fold induction. In conclusion, the ccMT-1 is a constitutively expressed MT and its gene promoter is inducible by various metal ions and chemical agents.

A single amino acid substitution can shift the optimum pH of DNase I for enzyme activity: biochemical and molecular analysis of the piscine DNase I family

We purified four piscine deoxyribonucleases I (DNases I) from Anguilla japonica, Pagrus major, Cryprus carpio and Oreochromis mossambica. The purified enzymes had an optimum pH for activity of approximately 8.0, significantly higher than those of mammalian enzymes. cDNAs encoding the first three of these piscine DNases I were cloned, and the sequence of the Takifugu rubripes enzyme was obtained from a database search. Nucleotide sequence analyses revealed relatively greater structural variations among the piscine DNase I family than among the other vertebrate DNase I families. From comparison of their catalytic properties, the vertebrate DNases I could be classified into two groups: a low-pH group, such as the mammalian enzymes, with a pH optimum of 6.5-7.0, and a high-pH group, such as the reptile, amphibian and piscine enzymes, with a pH optimum of approximately 8.0. The His residue at position 44 of the former group is replaced by Asp in the latter. Replacement of Asp44 of piscine and amphibian DNases I by His decreased their optimum pH to a value similar to that of the low-pH group. Therefore, Asp44His might be involved in an evolutionarily critical change in the optimum pH for the activity of vertebrate DNases I.

Effect of Pseudomonas aeruginosa (MTCC 1688) on the tissue phosphatases activity on Macrobrachium rosenbergii (De Man)

A time course study on the endotoxin toxicity of the gram negative bacteria, Pseudomonas aeruginosa MTCC 1688 on the tissue phosphatases activity on the giant freshwater prawn, Macrobrachium rosenbergii was conducted. The results revealed marked elevation of both acid and alkaline phosphatase activity in the haemolymph and body muscle. The hepatopancreas showed reduced phosphatase activity compared to control. The enzymes, being non-specific in action and particularly the acid phosphatase being of lysosomal origin, their increase in muscle and haemolymph has pathogenic significance in the inoculum treated prawns.

Todarepsin, a new cathepsin D from hepatopancreas of Japanese common squid (Todarodes pacificus)

An intracellular aspartic proteinase obtained from the hepatopancreas (liver) of Japanese common squid (Todarodes pacificus) was purified to homogeneity. The molecular mass of the enzyme was 36,500 Da on SDS-PAGE, and the isoelectric point was 8.29 by isoelectric focusing. The enzyme activity was optimal at pH 3.5, pH 2.2 and pH 3.0 for the substrates acid-denatured hemoglobin, acid-denatured casein, and MOCAc-GKPILFFRLK(Dnp)-D-R-NH2, respectively. Enzyme activity decreased rapidly at 50 degrees C. The Km and kcat values of the enzyme were estimated to be 3.2 mM and 46 s(-1) with MOCAc-GKPILFFRLK(Dnp)-D-R-NH2, and 1.7 mM and 1.1 s(-1) with MOCAc-SEVNLDAEFRK(Dnp)RR-NH2. The enzyme activity was strongly inhibited by pepstatin A, but only partially inhibited by DAN and EPNP. The Ki values for pepstatin A, DAN and EPNP were 0.5 nM, 0.5 mM and 0.2 mM, respectively. A cDNA encoding the enzyme was cloned by RT-PCR and subjected to nucleotide sequencing. The entire open reading frame was 1179 bp and coded for a protein of 392 amino acid residues. The mature enzyme consisted of 334 amino acids. The deduced amino acid sequence of the enzyme showed a high degree of identity to the sequences of cathepsins D found in various species.

Molecular characterization of D-amino acid oxidase from common carp Cyprinus carpio and its induction with exogenous free D-alanine

A full-length cDNA encoding D-amino acid oxidase (DAO, EC 1.4.3.3) was cloned and sequenced from the hepatopancreas of carp fed a diet supplemented with D-alanine. This clone contained an open reading frame encoding 347 amino acid residues. The deduced amino acid sequence exhibited about 60 and 19-29% identity to mammalian and microbial DAOs, respectively. The expression of full-length carp DAO cDNA in Escherichia coli resulted in a significant level of protein with DAO activity. In carp fed the diet with D-alanine for 14 days, DAO mRNA was strongly expressed in intestine followed by hepatopancreas and kidney, but not in muscle. During D-alanine administration, DAO gene was expressed quickly in hepatopancreas with the increase of DAO activity. The inducible nature of carp DAO indicates that it plays an important physiological role in metabolizing exogenous D-alanine that is abundant in their prey invertebrates, crustaceans, and mollusks.

Effects of nonylphenol and phytoestrogen-enriched diet on plasma vitellogenin, steroid hormone, hepatic cytochrome P450 1A, and glutathione-S-transferase values in goldfish (Carassius auratus)

The effects of nonylphenol (NP) on plasma vitellogenin (VTG) and steroid hormone values, as well as hepatic cytochrome P450 1A (CYP1A) and glutathione-S-transferase (GST) activities, were measured in goldfish (Carassius auratus) fed a diet with a low (formulated diet, FD) or high (commercial diet, CD) content of phytoestrogens, including genistein and daidzein. Male goldfish with secondary sexual characteristics were exposed to nominal NP concentrations of 0.1, 1.0, 10, and 100 microg/L in the water for 28 days while being fed either the FD or CD diet at 1.0% of body weight daily. Plasma VTG concentration in male goldfish exposed to 100 microg of NP/L and fed FD was significantly higher than that in the FD-fed control fish at seven, 21, and 28 days. However, fish of the CD-fed group exposed to 100 microg of NP/ L had significantly higher plasma VTG concentration than did fish of the CD-fed control group at 28 days only. Moreover, plasma VTG concentration in fish of the CD-fed control group was about 100-fold higher than that in fish of the FD-fed control group. Although the estrogenic effects of a phytoestrogen-enriched diet caused a decrease in testosterone and/or 11-ketotestosterone values in the CD-fed fish, there was no dose-response relationship between androgen and amount of NP to which the FD-fed fish were exposed. Nonylphenol does not have appreciable effects on hepatic CYP1A and GST activities in male goldfish at concentrations as low as 100 microg/L. These results suggest that NP has estrogenic activity in male goldfish at the nominal concentration of 100 microg/L, and that phytoestrogens, such as genistein and daidzein, in the CD inhibit an aspect(s) of steroid release and/or synthesis common to testosterone and 11-ketotestosterone. However, results of in vivo screening assays for endocrine-disrupting chemicals may be seriously affected by phytoestrogens in the diet, depending on content or potency of estrogenic activity; therefore, we recommend use in research of a standardized, open-formula diet in which estrogenic substances have been reduced to amounts that do not alter the results of studies that are influenced by exogenous estrogens.

Isolation of a Cadmium-releasing Bacterium and Characterization of Its Novel Protease

Microorganisms were screened for their ability to release cadmium from scallop hepatopancreas, which is the main residue after removing of the edible parts of scallop. The isolated strain, 23-0-11, identified as Arthrobacter nicotinovorans, secreted a protease which released cadmium from scallop hepatopancreas into the liquid medium. The molecular mass of the enzyme was estimated to be 27 kDa. The sequence of the 15 N-terminal amino acids of the protease showed no close similarity with any other protein. Compared with a commercial enzyme, the purified protease had greater ability to release cadmium. The enzyme activity was greatest at 50 degrees C and pH 7.0, and was enhanced in the presence of Ca(2+), Mg(2+) and Mn(2+), while being strongly inhibited by Co(2+). The inhibition profile by the serine protease inhibitor, phenylmethylsulphonyl fluoride (PMSF), confirmed that the protease belonged to the serine protease family.

cDNA cloning of an alginate lyase from abalone, Haliotis discus hannai

An alginate lyase, termed HdAly in the present paper, was isolated from the hepatopancreas of abalone, Haliotis discus hannai, by ammonium sulfate fractionation, followed by TOYOPEARL CM-650M column chromatography. Enzymatic properties of HdAly were similar to those of previously reported Haliotis and Turbo poly(M) lyases, e.g., it preferentially degraded a poly(beta-D-mannuronate)-rich substrate with an optimal pH and temperature at pH 8.0 and 45 degrees C, respectively. In order to determine the primary structure of abalone lyase that is still poorly understood, cDNAs for HdAly were cloned by PCR from the abalone hepatopancreas cDNA library and sequenced. From the nucleotide sequences of the cDNAs, the sequence of 909 bp in total was determined, and the amino acid sequence of 273 residues was deduced from the translational region of 822 bp locating at nucleotide positions 27-848. The N-terminal region of 16 residues, except for the initiation Met in the deduced sequence, was regarded as the signal peptide since it was absent in the HdAly protein and showed high similarity to the consensus sequence for signal peptides of eukaryote secretary proteins. This suggests that HdAly is initially produced as a precursor possessing the signal peptide in hepatopancreatic cells and then secreted into digestive tract as the mature form. Thus, the mature HdAly was regarded to consist of 256 residues with the calculated molecular mass of 28895.5 Da. The amino acid sequence of HdAly showed 85 and 28% identity to those of Turbo cornutus alginate lyase SP2 and the C-terminal region of Chlorella virus lyase-like protein CL2, respectively, while it showed no significant identity to those of any bacterial alginate lyases. In order to provide the basis for the structure-function studies and various applications of the abalone lyase, a bacterial expression system was constructed by means of the HdAly-cDNA and pET-3a expression plasmid. Although the active recombinant HdAly was hardly produced at a cultivation temperature 37 degrees C in Escherichia coli BL21 (DE3), a small amount of soluble and active enzyme could be produced when the temperature was lowered to 19 degrees C.

[Chitosan depolymerization by enzymes from hepatopancreas of the crab Paralithodes camtschaticus]

An enzyme preparation was isolated from the Paralithodes camtschaticus hepatopancreas that exhibited chitinase and chitosanase activities. Treatment of chitin and chitosan with this preparation decreased their viscosity-average molecular weights by 96 and 41%, respectively. The chromatographic profiles of the products of chitin and chitosan hydrolysis suggested that the crab hepatopancreas in rich in endochitinases. Enzymatic digestion of chitosan increased its solubility and moderately reduced the extent of its acetylation. A mathematical approach was proposed for calculating the molecular weights of chitosan fractions from weight-average molecular weights determined viscometrically.

Changes in cell type composition and enzymatic activities in the hepatopancreas of Marsupenaeus japonicus during the moulting cycle

The goal of the present study was to evaluate the changes in the cell type composition and ATPase activities (total ATPase, ouabain-sensitive Na+/K(+)-ATPase, furosemide-sensitive Na(+)-ATPase) that occur during the different stages of the moulting cycle in the hepatopancreas of the Marsupenaeus japonicus. The results clearly suggest that the number of resorptive and fibrillar cell types changes significantly during the different stages. An inverse correlation between resorptive and fibrillar cells is observed during moulting (both in normally fed and fasted animals). Fasting, but not the moulting cycle, affects the number of blister-like cells. In the resorptive cells the enzymatic activities (total ATPases and ouabain-sensitive Na+/K(+)-ATPase) also change during the moulting in a cyclical manner. All these results are in agreement with and confirm the different functions carried out by the two cell types within the hepatopancreas.

Purification and characterization of an alpha-glucosidase from the hepatopancreas of the shrimp Penaeus japonicus (Crustacea: decapoda)

1. The alpha-glucosidase purified from the hepatopancreas of Penaeus japonicus is not membrane-bound and labile to heating at 65 degree C for 10 min. 2. The specific activity of the purified enzyme is 223 units/mg of protein. After polyacrylamide gel electrophoresis under denaturing conditions, the purified alpha-glucosidase from shrimp was found to consist of monomers of M(r) 105,000. 3.The alpha-glucosidase from shrimp has an isoelectric point (pI) of 3.8 and becomes more alkaline after the removal of sialic acid and phosphoric acid. 4.The shrimp enzyme has the pH optimum at 5.0 and its K(m) was 125 micrometer with 4-methylumbelliferyl-alpha-D-glucoside as substrate.

Comparative study of free and membrane-bound acidic beta-D-glucosidase from the hepatopancreas of the shrimp Penaeus japonicus (Crustacea: decapoda)

l. In the hepatopancreas of the shrimp Penaeus japonicus the beta-glucosidase is present, either free or membrane-bound. The specific activity of the purified enzyme is 237,333 units/mg of protein and 191,111 units/mg of protein for the free and the membrane-bound beta-glucosidase, respectively. 2.The non-membrane-bound beta-glucosidase appears to be the same molecular size as the membrane-bound enzyme, both being monomers and consisting of a polypeptide chain of apparent M(r) 65,000, as estimated by chromatography on Superose 12 and by SDS-PAGE. 3.Both enzymes share similarities in their molecular size and substrate specificities (with ratios of 100:17:4:12 for the non-membrane-bound and 100:32:13:12 for the membrane-bound enzyme for the activities with methylumbelliferyl-beta-D-glucoside, methylumbelliferyl-beta-D-galactoside, methylumbelliferyl-alpha -L-arabinopyranoside and methylumbelliferyl-beta-xyloside respectively, as substrates). 4.The membrane-bound beta-glucosidase can be differentiated from the non-membrane-bound enzyme by its isoelectric point (7.5 vs 6.6), Km (182 micrometer vs 76 micrometer), pH optimum (4.5 vs 5.5), phosphorylation,sialyation and thermostability.

A neutral beta-galactosidase from the hepatopancreas of the shrimp Penaeus monodon (Crustacea: Decapoda): dimeric and sialyated

1. A beta-galactosidase was purified ca 245-fold to homogeneity from Penaeus monodon, with a final spec. act. of 61.3 U/mg of protein. 2.By using SDS-polyacrylamide gel electrophoresis, the monomers of shrimp beta-galactosidase were discovered to have mol. wts of 31,000 and those of human placental enzyme, 32,000. Since the active shrimp beta-galactosidase was found to have a mol. wt of 66,000 by AcA 34 gel filtration chromatography,it was concluded that the purified shrimp enzyme was dimeric. 3.In contrast to the discovery of thermostability with human placental beta-galactosidase, the shrimp enzyme was found to be unstable to heating at 45 degree C for 10 min. Both enzyme activities were inhibited by Mn (2+) and Zn (2+) ions.4. The shrimp beta-galactosidase has an isoelectric point (pI) of 7.0, but the human placental enzyme has a pI of 5.5. Both enzymes were sialyated. 5.The shrimp beta-galactosidase has a pH optimum at 7.0 and its K(m) was 1.9 micrometer with 4-methylumbelliferyl-beta-D-galactoside as substrate. The human enzyme has pH optimum at 7.0 or 4.0, and its K(m) was 9.8 micrometer.