Phosphonosphingoglycolipid,a novel sphingolipid from the viscera of Turbo cornutus

A novel lipid which contained long-chain base, fatty acid, galactose and N-methylaminoethylphosphonic acid in an equimolar was isolated from the viscera of Turbo cornutus.The methods used for the structural elucidation of this lipid were partial acid hydrolysis, alkaline hydrolysis, periodate oxidation and Smith degradation. The structure of breakdown products were mainly identified by combined gas chromatography and mass spectrometry.The structure of the novel lipid was determined to be 1-O-[6′-O-(N-methylaminoethylphosphonyl) galactopyranosyl] ceramide.Mass spectra of galactose-N-methylaminoethylphosphonate and glycerol-N-methylaminoethylphosphonate are given.     

Isolation and some properties of a deoxyribonuclease from Turbo cornutus.

1. Four DNases were found in the dried liver extract of a top shell, Turbo cornutus. The major one was purified 120-fold by phosphocellulose column chromatography, sulfoethylcellulose column chromatography and gel-filtration on Sephadex G-150. The yield was 2.7%. 2. The enzyme activity was not affected by Mg2+ (10(-3)--10(-2)M), EDTA (10(-3)--10(-2)M), or NaCl (10(-1)M). It showed a pH optimum of 4.7--4.8. Ionic strength was found to be critical for the maximal activity. The isoelectric point was 8.5--9.0. On heating at 50 degrees C C for 5 min the enzymic activity fell to half the initial value. 3. The enzyme preparation degraded native as well as heat-denatured DNA, but not RNA. It degraded heat-denatured DNA endonucleolytically to give oligonucleotides with 3'-phosphates. 4. The 3'-phosphate and 5'-hydroxy termini of oligonucleotides were investigated. At both the 3'- and 5'-terminal positions, purine nucleotides were predominant.     

Purification and properties of two isoenzymes of beta-N-acetylhexosaminidase from Turbo cornutus.

1. beta-N-acetylhexosaminidase isoenzymes from the gastropod, T. cornutus, were purified and their properties studied. 2. The two isoenzymes, designated A and B were separated by DEAE-Sephadex column chromatography and further purified by CM-cellulose, Concanavalin-A-Sepharose-4B and Sephadex G-200 column chromatography. 3. beta-N-Acetylhexosaminidase A and B were purified 416 and 208 fold, with yields of 10.6 and 5.1%, respectively. 4. The two isoenzymes appear homogeneous on polyacrylamide gel electrophoresis, with the A form migrating faster towards the anode than the B form. 5. The purified isoenzymes are virtually free of all other common glycosidase contaminations. 6. The apparent molecular weight of both beta-N-acetylhexosaminidase A and B is about 100,000 when estimated with gel filtration column chromatography and the pH optimum for both is 4.0. 7. Both beta-N-acetylhexosaminidase isoenzyme activities are stimulated by Cl-, Br-, F-, I- and NO3-, and inhibited by Hg+, Ag+, Fe3+, N-acetylglucosamine and N-acetylgalactosamine. 8. The Km values of beta-N-acetylhexosaminidase A and B for the substrate p-nitrophenyl-beta-2-acetamide-2-deoxy-D-glucopyranoside were 2.9 and 3.2 mM, respectively.     

The chemical modification of the essential groups of beta-N-acetyl-D-glucosaminidase from Turbo cornutus Solander

The chemical modification of beta-N-acetyl-D-glucosaminidase (EC3.2.1.30) from Turbo cornutus Solander has been first studied. The results demonstrate that the sulfhydryl group of cysteine residues and the hydroxyl group of serine residues are not essential to the enzyme's function. The modification of indole group of tryptophan of the enzyme by N-bromosuccinimide (NBS) can lead to the complete inactivation, accompanying the absorption decreasing at 278 nm and the fluorescence intensity quenching at 335 nm, indicating that tryptophan is essential residue to the enzyme. The modification of amino group of lysine residue by formaldehyde and trinitrobenzenesulfonic acid also inactivates the enzyme completely. The results show that lysine and tryptophan are probably situated in the active site of the enzyme. The modification of the imidazole residue and carboxyl group leads to inactivate incompletely, indicating they are not the composing groups of the enzyme active center, and they are essential for maintaining the enzyme's conformation which is necessary for the catalytic activity of the enzyme.     

Effect of immobilization on stability and kinetic properties of alpha-L-fucosidase from Turbo cornutus

An amount of alpha-L-fucosidase from T. cornutus liver was copolymerized with glutaraldehyde using bovine serum albumin as the carrier protein. The properties of the native, the soluble enzyme polymer complex, and the insoluble enzyme polymer complex were studied and compared under various conditions of pH, temperature, substrate, and inhibitor concentration. Native alpha-L-fucosidase was heat labile and lost more than 85% of its activity when incubated at 55 degrees C for 5 min. In contrast, under equivalent incubation conditions, both the soluble and the insoluble enzyme polymer complexes exhibited enhanced resistance to thermal inactivation and after 5 min lost only 65 and 40% of their original activity, respectively. Polymerzation also resulted in the shift of pH optima towards the acidic range, a decrease in activation energy and a change in the apparent K(m) values towards the p-nitrophenyl-alpha-L-fucopyranoside substrate.     

Isolation and Properties of Alginate Lyase from the Mid-Gut Gland of Wreath Shell Turbo cornutus

Alginate lyase [EC 4.2.2.3] has been purified from mid-gut gland of wreath shell. The enzyme was homogeneous as judged by SDS-polyacrylamide gel electrophoresis. A molecular weight of 32,000 was estimated by SDS-polyacrylamide gel electrophoresis. Absorption spectra of the reaction products indicated that the enzyme had lyase activity. The enzyme was most active at a pH range of about 8.8 to 9.2 and most stable at pH 5 to 6. Phosphate showed strong stabilizing and enhancing effects on the enzyme activity. Divalent cations behaved differently toward alginic acid and propylene glycol alginate, suggesting requirements for free carboxyl groups and a single glycosidic chain in the enzyme action.     

Isolation and Purification of Vitelline-Coat Lysin from Testis of Turbo cornutus (Mollusca)

A substance causing swelling of the vitelline coat (vitelline-coat lysin) was extracted from the testis of a sea snail, Turbo cornutus. Its activity was quantified by a volumetric method using a suspension of vitelline coat isolated from T. cornutus eggs. The lysin was purified 50-fold by hydroxyapatite and Bio-Gel P-10 column chromatographies and the final preparation appeared homogenous on sodium dodecyl sulfate polyacrylamide gel electrophoresis. Its molecular weight was estimated to be 18,500 by sodium dodecyl sulfate polyacrylamide gel electrophoresis, and 18,000 by sedimentation equilibrium analysis. These results suggested that the lysin exists as a monomeric molecule. Its isoelectric point was p^H 6.4. The lysin contained residues of most common amino acids except cystine and cysteine, with relatively high proportions of lysine, aspartic acid and leucine. The N-terminal amino acid was identified as serine. The lysin loosened the fibrous structure of the vitelline coat without releasing any soluble product and seemed to act by a stoichiometric, nonenzymatic mechanism.     

Isozymes of Alginate Lyase in the Mid-gut Gland of Turbo cornutus

Alginate lyase, SP2, from Turbo cornutus was separated on an SP-Sephadex C-50 column from SP1, whose properties have already been reported, and purified according to the method employed for SP1, to obtain information on SP2. The profiles of the optimal pH, pH-stability, thermal inactivation and molecular size of SP2 were entirely the same as those of SP1. The isoelectric point of SP1 and SP2 was 7.5 and 7.7, respectively. The action of SP2 on Alginate caused a rapid decrease in solution viscosity. Analysis of digestion products of alginate with SP2 showed that the enzyme had an affinity toward the mannuronate-rich domains of the alginate molecule and released unsaturated oligomers mostly composed of mannuronic acid as final product. Alginate lyases, SP1 and SP2, were shown to be isozymes in the mid-gut gland of Turbo cornutus.     

Coiled Filamentous Structure in the Sperm Acrosome of Gastropoda, Sulculus aquatilis and Turbo cornutus

A helically coiled filamentous structure, termed the truncated cone originally identified in Haliotis discus , was demonstrated to exist in the apex of the acrosome subjacent to the outer acrosomal membrane of the sperm in two species of Gastropoda, Sulculus aquatilis and Turbo cornutus . Thin section and whole mount preparations revealed that in intact sperm this filamentous structure consisted of about 12 helically arranged filaments with a diameter of 10–12 nm which were tightly packed in a truncated shape. This truncated cone elongated anteriorly from the acrosomal opening and transformed into a cylinder which closely surrounds the acrosomal process during the acrosome reaction. In S. aquatilis and T. cornutus , the truncated cone elongated more than 3 and 1.5 times as long as the original height, respectively. The elongated truncated cone was characterized by striations with increase in its periodic spacing and inclinations in thin sections. The truncated cone in both the species was fundamentally analogous to that of Haliotis discus , further suggesting that the truncated cone plays a role in fertilization as a common cytoskeletal structure among the species of Gastropoda.     

Amino Acid Sequence, Spectral, Oxygen-Binding, and Autoxidation Properties of Indoleamine Dioxygenase-Like Myoglobin from the Gastropod Mollusc Turbo cornutus

Myoglobin was isolated from the radular muscle of the archaeogastropod mollusc Turbo cornutus (Turbinidae). This myoglobin is a monomer carrying one protoheme group; the molecular mass was estimated by SDS–PAGE to be about 40 kDa, 2.5 times larger than that of usual myoglobin. The cDNA-derived amino acid sequence of 375 residues was determined, of which 327 residues were identified directly by chemical sequencing of internal peptides. The amino acid sequence of Turbo myoglobin showed no significant homology with any other usual 16-kDa globins, but showed 36% identity with the myoglobin from Sulculus diversicolor (Haliotiidae) and 27% identity with human indoleamine 2,3-dioxygenase, a tryptophan-degrading enzyme containing heme. Thus, the Turbo myoglobin can be counted among the myoglobins which evolved from the same ancestor as that of indoleamine 2,3-dioxygenase. The absorbance ratio of γ to CT maximum (γ/CT) of Turbo metmyoglobin was 17.8, indicating that this myoglobin probably possesses a histidine residue near the sixth coordination position of heme iron. The Turbo myoglobin binds oxygen reversibly. Its oxygen equilibrium properties are similar to those of Sulculus myoglobin, giving P ₅₀ = 3.5 mm Hg at pH 7.4 and 20°C. The pH dependence of autoxidation of Turbo oxymyoglobin was quite different from that of mammalian myoglobin, suggesting a unique protein folding around the heme cavity of Turbo myoglobin. A kinetic analysis of autoxidation indicates that the amino acid residue with pK _a = 5.4 is involved in the reaction. The autoxidation reaction was enhanced markedly at pH 7.6, but not at pH 5.5 and 6.3 in the presence of tryptophan. We suggest that a noncatalytic binding site for tryptophan, in which several dissociation groups with pK _a ≥ 7.6 are involved, remains in Turbo myoglobin as a relic of molecular evolution.     

Structural studies on glycolipid of shellfish. III. Novel glycolipids from Turbo cornutus

Five kinds of sphingoglycolipids were isolated from Turbo cornutus. Four of them were a series of novel glycolipids consisting only of galactose. The structures of these glycolipids were studied by methylation analysis, periodate oxidation, enzymatic degradation, and proton magnetic resonance spectroscopy. Three glycolipids were characterized as galactosyl(beta 1 leads to 1)ceramide, galactosyl(beta 1 leads to 6)galactosyl(beta 1 leads to 1)ceramide, and galactosyl(beta 1 leads to 6)galactosyl(beta 1 leads to 6)galactosyl(beta 1 leads to 1)ceramide. Data indicating that the 4th glycolipid might be the tetragalactosyl derivative of this series were obtained. The carbohydrate moiety of the 5th glycolipid, in contrast, was composed of fucose, galactose, glucose and N-acetylglycosamine in a molar ratio of 1 : 2 : 1 : 1.     

A beta-galactosidase isoenzyme from Turbo cornutus with substrate specificity toward GM1-ganglioside and glycoproteins

beta-Galactosidase from T. cornutus was resolved into two activity peaks by gel filtration column chromatography. The pH optima of the two peaks designated P1 and P2, were 5.5 and 3.0, respectively, when p-nitrophenyl-beta-D-galactopyranoside was used as the substrate. The molecular weights of P1 and P2 were 700,000 +/- 70,000 and 78,000 +/- 7800, respectively, when estimated by gel filtration chromatography. The activities of both forms of the enzymes are stimulated by anions such as Cl-, Br- and NO-3. While the activity of P1 was stimulated by low anion concentrations, P2 requires 700 times higher anion concentration for similar enhancement of activity. P1, the high molecular weight form hydrolyzes mainly galactose from small molecular weight beta-galactosides, such as p-nitrophenyl-beta-D-galactopyranoside, 4-methylumbelliferyl-beta-D-galactopyranoside, lactose, lactosylceramide and 3-O-beta-D-galactopyranosyl-D-arabinose, whereas P2, the low molecular weight form cleaves, in addition, all the beta-galactosides tested, including 2-hexadecanoylamino-4-nitrophenyl-beta-D-galactopyranoside, GM1-ganglioside, asialo-GM1-ganglioside, asialo fetuin, alpha 1-acid glycoproteins and the tryptic peptides of the glycoproteins. The optimal conditions for the hydrolysis of the terminal galactose from GM1-ganglioside which does not occur in gastropods, such as T. cornutus, was found to require 40 mM NaCl and 1 mM sodium taurodeoxycholate at pH 3.0 in 50 mM sodium citrate buffer, conditions similar to those by mammalian beta-galactosidase.     

Inhibitory activity of brown algal phlorotannins against glycosidases from the viscera of the turban shell Turbo cornutus

The crude phlorotannins from the brown alga Eisenia bicyclis showed inhibitory activity against 10 of 13 kinds of glycosidases present in the viscera of the turban shell Turbo cornutus. Phloroglucinol and its oligomers – eckol (a trimer), phlorofucofuroeckol A (a pentamer), dieckol and 8,8′-bieckol (hexamers), and an unidentified tetramer – were isolated from the crude phlorotannins by column and thin-layer chromatography. Phlorofucofuroeckol A, dieckol and 8,8′-bieckol inhibited α-fucosidase, β-galactosidase and β-mannosidase partially purified from T. cornutus, while phloroglucinol, eckol and the unidentified tetramer were weakly active. Dieckol was a competitive inhibitor of α-fucosidase with an inhibition constant (K _i) of 0.12?mM. The amounts of phlorotannins released after the immersion of freshly collected E. bicyclis in seawater or deionized water were estimated by high-performance liquid chromatography. Nearly all the phlorotannins were exuded into the medium following the death of the algae, whereas no phlorotannins were detected in the medium of living algae. These findings indicate that the phlorotannins deter the feeding of marine herbivorous gastropods by inhibiting the glycosidases.     

Inhibition of evoked neurotransmitter release from rat hippocampus by a polypeptide toxin isolated from the marine snail Conus distans.

The active fraction, isolated and partially purified from the crude venom of the marine snail Conus distans, with a molecular mass of about 25 kDa, inhibits neurotransmitter release in rat hippocampus. This toxin (distans Toxin) inhibits the electrically evoked tritium labelled noradrenaline release from rat hippocampal slices in a dose and time dependent manner. The neurotransmitter release is mainly regulated by N-type of voltage sensitive Ca(2+)-channels. The distans toxin behaves as a partial antagonist of calcium in the buffer, possibly by competing with calcium for this type of voltage sensitive Ca(2+)-channels.     

Purification, subunit structure and pharmacological effects on cardiac and smooth muscle cells of a polypeptide toxin isolated from the marine snail Conus tessulatus

The most active component in smooth muscle contraction, isolated from the whole venom of the marine snail Conus tessulatus, has a molecular mass of about 55 kDa. The toxin protein, tessulatus toxin, appeared to be constituted by two distinct polypeptide bands of 26 kDa and 29 kDa. The pure toxin caused a marked contraction of both guinea-pig ileum and rabbit aorta at nanomolar concentrations. Tessulatus-toxin-induced contraction was indirectly prevented by classical inhibitors of the voltage-dependent Ca2+ channel. Tessulatus toxin caused a large increase in the initial rate of 45Ca2+ uptake by cardiac cells. This uptake was insensitive to Ca2+ channel blockers at concentrations 100-1000 fold higher than those known to block voltage-dependent Ca2+ channels in these cells. Voltage clamp experiments have confirmed that tessulatus toxin was not directly active on the Ca2+ current. Tessulatus-toxin-stimulated 45Ca2+ influx was inhibited by dichlorobenzamil and suppressed when Na+ was substituted by Li+, indicating that the toxin acted via activation of the Na+/Ca2+ exchange system in cardiac cells. Activation by tessulatus toxin of the Na+/Ca2+ exchange system occurred via a toxin-stimulated Na+ entry into cardiac cells and was observed in the same range of toxin concentration which produced 45Ca2+ entry. The Na+ entry system that was activated by tessulatus toxin was insensitive to classic inhibitors of known Na+ entry systems in cardiac cells. Possible mechanisms by which tessulatus toxin induced Na+ entry into cardiac cells and contractions in smooth muscles are discussed. Tessulatus toxin is cytotoxic when used at high concentrations.