Comparative Biochemistry and Physiology Part B: Comparative Biochemistry最新文献

A levamisole-sensitive (K_i = 0.72 mM) alkaline phosphatase (pH optimum 9.1) and a levamisole-insensitive alkaline phosphatase (pH optimum 7.1) are present in gills of the blue crab Callinectes sapidus. Both enzymes are distinct from ouabain-sensitive ATPase. Specific activity for either phosphatase is greatest in the acinar tissue, which lines the branchial vessels. Histochemical localization of the enzymes confirmed this distribution. Activity of levamisole-sensitive alkaline phosphatase is affected by acclimation salinity. V_max of the levamisole-sensitive alkaline phosphatase is greater in high-salinity crabs than in low-salinity crabs; apparent K_m is not significantly different. The levamisole-sensitive alkaline phosphatase associated with the acinar tissue lining the branchial vessels may modulate the osmoregulatory response in blue crabs.

A juvenile hormone binding protein (JHBP) has been isolated from Bombyx mori hemolymph by gel filtration, ion-exchange chromatography, chromatofocusing and hydroxyapatite column chromatography. Gel electrophoresis indicates that the isolated protein is homogeneous in the presence or absence of a denaturing agent. The JHBP in question has a relative molecular mass of 32 kDa, determined by denaturing gel electrophoresis. Chromatofocusing analysis indicated that the JHBP is an acidic protein with pI 4.9. The protein exhibits a dissociation constant of 9.0 × 10⁻⁸ M for JH I, 1.14 × 10⁻⁷ M for JH II and 3.9 × 10⁻⁷ M for JH III, and thus its affinity for JH analogues is in the order of JHI >JHII >JHIII. Its amino acid composition indicates that the protein consists of 297 residues of 18 kinds of amino acids. The sequence of the N-terminus of the polypeptide chain was determined for 34 of the first 36 residues: Asp-Gln-Asp-Ala-Leu-Leu-Lys-Pro-?-Lys-Leu-Gly-Asp-Met-Gln-Ser-Leu-Ser-Ser-Ala-Thr-Gln-Gln-Phe-Leu-Glu- Lys-Thr-Ser-Lys-Gly-Ile-Pro-?-Tyr-His-.

A new mannan-binding lectin (MBL) and a previously described fucose-binding lectin (FBL) have been isolated from serum of Anguilla anguilla by affinity chromatography on A-peptone-Sepharose in combination with electroelution (MBL) or affinity chromatography using α-l-fucose-agarose (FBL). MBL has a mol. wt of approximately 246,000 and is composed of identical subunits of approximately 24,000, two of each are always covalently linked. FBL has a mol. wt of about 121,000 and consists of four subunits of 30,000, which, upon reduction are split into two identical subunits of 15,000. Upon isoelectric focusing MBL displays four bands ranging from pH 4.8 to 5.2 FBL shows 17–20 bands between pH 5.5 and 6.2. Of the inhibitors utilized, hemagglutination activity of MBL is inhibited only by mannan, whereas FBL activity is inhibited by several glycosubstances. MBL and FBL activity is constant between pH 4 and 10 and 5 and 10, respectively. Temperatures above 55°C totally destroy MBL activity whereas FBL activity remains constant up to 75°C.

Live tapeworms have been fixed to retain antigenicity of their proteins, and subsequently prepared for electron microscopy. Thin sections of tapeworms were prepared from resin blocks. Sections were immunocytochemically labelled using a colloidal gold probe and viewed using transmission electron microscopy. Calmodulin was detected associated with cellular structures to which calmodulin has previously been linked in other higher eukaryotes. Calmodulin would appear to have a similar role of importance in tapeworms, as it does in higher eukaryotes although tapeworms are prevalently a syncitium.

Two enzymes possessing collagenolytic activity were isolated from the hepatopancreas of crab Paralithodes camtschatica by ammonium sulfate fractionation and DEAE-Sepharose chromatography. It was shown that the specific activities of proteases A and C toward insoluble collagen were equal to 400 and 300 Mandl units/mg protein, respectively. The mol. wt of homogenous proteases A and C determined by gradient polyacrylamide gel electrophoresis in the presence of SDS and 2-mercaptoethanol were equal to 30 and 24 kDa, respectively. The isoelectric point values for the enzymes were determined as 2.5 and 2.9. Both enzymes lack carbohydrates. The amino acid compositions of two crab proteases were measured. The optimal conditions for the enzyme catalysis and the catalytic constants for collagenolytic proteases A and C with respect to Bz-Arg-pNA and Bz-Tyr-OEt have been determined. Inhibition data led to classification of the purified enzymes as serine proteases.

Analyses were made of lipids extracted from the spermatozoa of the sea-urchins, Diadema setosum, Arbacia lixula, Paracentrotus lividus and Clypeaster japonicus which belong to the order Diadematoida, Arbacioida, Echinoida and Clypeasteroida, respectively. Diadema setosum and A. lixula spermatozoa contained several kinds of phospholipids (phosphatidylcholine, phosphatidylserine, phosphatidylethanolamine and caldiolipin), cholesterol and triglyceride. In addition to similar phospholipids, cholesterol and triglyceride, cholesterol-ester was also detected in C. japonicus spermatozoa. In contrast, lipids of P. lividus spermatozoa comprised phospholipids and cholesterol. In these species, the fatty acid composition of phosphatidylcholine, phosphatidylethanolamine and cardiolipin was of the unsaturated type for the most part, while phosphatidylserine and triglyceride, except in the case of P. lividus, comprised, to a considerable degree, saturated fatty acid.

Susceptibilities of various molluscan hosts to different strains of the parasites were reviewed. Cellular reactions following host-parasite associations were elucidated. Moreover, metabolic similarities, integration and biochemical adaptation of the parasite and host were also investigated in an attempt to elucidate factors affecting the host-parasite relationship.

The effects of pressure on pertussis toxin (PTX)-catalyzed [³²P]ADP-ribosylation of α-subunits of the guanine nucleotide-binding proteins, G_i and G_o, were examined in the presence of the guanyl nucleotides GDP and guanosine 5′-O-[γ-thio]triphosphate (GTPγS) in brain membrane preparations from two congeneric marine fish that live at different depths. In the presence of 100 μM GDP, pressures up to 340 atm had no effect on PTX-catalyzed [³²P]ADP-ribosylation in the deeper-occurring species, Sebastolobus altivelis. [³²P]ADP-ribosylation was suppressed 37% by 68 atm pressure in the shallower-living S. alascanus. Pressure in the range 204–476 atm inhibited the reaction approximately 54%. In the presence of 100 μM GTPγS, the effects of pressure were identical in the two species. Pressures of 68–340 atm inhibited [³²P]ADP-ribosylation approximately 30% in both species; 476 atm inhibited ribosylation 54%. In the shallower-living species, pressure may increase the fraction of G proteins coupled to unoccupied receptors or decrease the efficacy of GDP in promoting the heterotrimeric aggregation state. Pressure appears to enhance the efficacy of GTPγS in dissociating the heterotrimeric holoprotein in both species. The structural similarities of the G_i/G_o α-subunits of the two species were compared by mapping partial proteolytic digests of brain homogenates labeled with [³²P]ADP by PTX on sodium dodecyl sulfate-polyacrylamide gels. The proteases used were TPCK-treated trypsin, subtilisin Carlsberg and Staphylococcus aureus strain V8 endoproteinase Glu-C. The [³²P]ADP-labeled peptide maps of the two species were indistinguishable. The differences in pressure sensitivity between the two species may result from small changes in primary structure and/or post-translational modification of the heterotrimeric subunits.

The constitutive nitric oxide synthase activity of the catfish taste organ (barbel) was characterized, using the conversion of l-[³H]arginine to l-[³H]citrulline as the index of enzyme activity. The enzyme was dependent on Ca²⁺ (but not calmodulin) and NADPH (but not FAD). Activity was moderately enhanced by tetrahydrobiopterin. Kinetic parameters were K_m = 22 μM and V_max = 25 pmol/min/mg. The enzyme was inhibited by $\text{N}{}^{\mathrm{<mtext>G</mtext>}}\text{-}\text{monomethyl-}\text{l}\text{-arginine}$ (half-maximally at 3 μM) and $\text{N}{}^{\mathrm{<mtext>G</mtext>}}\text{-}\text{nitro-}\text{l}\text{-arginine}$ (half-maximally at 50 μM), and also by sodium nitroprusside and superoxide dismutase. In the presence of millimolar levels of the taste stimulus l-alanine, nitric oxide synthase activity was increased by up to 3-fold, with activation of the enzyme being reversed by $\text{N}{}^{\mathrm{<mtext>G</mtext><mtext>-monomethyl-</mtext><mtext>l</mtext><mtext>-arginine</mtext>}}$. There was no activation of guanylyl cyclase by l-alanine. These data indicate that a constitutive nitric oxide synthase activity is present in the catfish taste organ and that, therefore, nitric oxide may have a role in the biochemical mechanisms underlying taste perception.