Structures of the carbohydrate units of polysialoglycoproteins isolated from the eggs of four species of salmonid fishes

Fish egg polysialoglycoprotein (PSGP) is a novel type of 200 kDa-glycoprotein containing more than 50% sialic acid by weight and about 90O-glycosidically-linked sialoglycan units per molecule. Of about 100 different molecular species assumed to be present in a sialoglycan mixture obtained by alkaline borohydride treatment ofSalvelinus leucomaenis pluvius PSGP, 23 mono- to tetrasialylglycans were isolated by anion-exchange chromatography and preparative column chromatography on porous silica, and their structures were determined. Core asialo-oligosaccharides were obtained from PSGP of four species of salmonid fishes by exhaustive enzymatic desialylation of sialoglycan mixtures and the structures of purified compounds were determined. Two complete types of asialopentasaccharide core structures, Fuc1-3GalNAc1-3Gal1-4 Gal1-3GalNAcOL, and GalNAc1-4GalNAc1-3Gal1-4Gal1-3GalNAcOL, and all of the possible biosynthetic precursors of these pentasaccharide cores were found in every PSGP examined. All types of oligosaccharide chains, both complete and incomplete, were found to occur in highly sialylated forms in PSGP.Abbreviations NeuAc N-acetylneuraminic acid - NeuGc N-glycolylneuraminic acid - GalNAcOL N-acetylgalactosaminitol - PSGP polysialoglycoprotein - SRO sialidase-resistant oligosaccharide     

Relationship between Photosynthesis and Chlorophyll Content during Leaf Senescence of Rice Seedlings

Photosynthetic oxygen evolution, chlorophyll contents and chlorophylla /b ratios of 3rd to 6th leaves of rice seedlings were measuredto examine whether or not inactivation of photosynthesis duringsenescence is related to loss of chlorophyll. Photosyntheticactivity decreased more rapidly than chlorophyll content duringleaf senescence; as a result, the lower the leaf position, thelower was the rate of oxygen evolution determined on the basisof chlorophyll. Chlorophyll ab ratio also decreased with advancingsenescence. Electrophoretic analysis revealed that the declinein chlorophyll ab ratio is due to more rapid degradation ofthe reaction center complexes than light-harvesting chlorophyllab proteins of photosystem II and that the photosystem I reactioncenter disappears in parallel with the inactivation of photosynthesis.A simple method was developed to estimate the amounts of chlorophylla associated with the reaction center complexes of the two photosystemsfrom the total chlorophyll contents and chlorophyll ab ratiosof leaves. Rates of oxygen evolution, determined on the basisof chlorophyll a bound to the reaction center complexes, remainedconstant throughout the course of senescence. Thus, inactivationof photosynthesis is closely related with loss of the reactioncenter complexes during leaf senescence of rice seedlings. Theresults suggest that loss of photosynthesis is mainly causedby loss of a functional unit of photosynthesis or by a decreasein the number of whole chloroplasts. (Received April 22, 1987; Accepted August 13, 1987)     

Angiotensin III: A Potent Inhibitor of Enkephalin-Degrading Enzymes and an Analgesic Agent

Various angiotensins, bradykinins, and related peptides were examined for their inhibitory activity against several enkephalin-degrading enzymes, including an aminopeptidase and a dipeptidyl aminopeptidase, purified from a membrane-bound fraction of monkey brain, and an endopeptidase, purified from the rabbit kidney membrane fraction. Angiotensin derivatives having a basic or neutral amino acid at the N-terminus showed strong inhibition of the aminopeptidase. Dipeptidyl aminopeptidase was inhibited by angiotensins II and III and their derivatives, whereas the endopeptidase was inhibited by angiotensin I and its derivatives. The most potent inhibitor of aminopeptidase and dipeptidyl aminopeptidase was angiotensin III, which completely inhibited the degradation of enkephalin by enzymes in monkey brain or human CSF. The Ki values for angiotensin III against aminopeptidase, dipeptidyl aminopeptidase, endopeptidase, and angiotensin-converting enzyme, which degraded enkephalin, were 0.66 X 10(-6), 1.03 X 10(-6), 2.3 X 10(-4), and 1.65 X 10(-6) M, respectively. Angiotensin III potentiated the analgesic activity of Met-enkephalin after intracerebroventricular coadministration to mice in the hot plate test. Angiotensin III itself also displayed analgesic activity in that test. These actions were blocked by the specific opiate antagonist naloxone.     

A novel type of aryl sulfotransferase obtained from an anaerobic bacterium of human intestine

A novel type of aryl sulfotransferase is produced by an anaerobic bacterium of human intestine, Eubacterium A-44. Aryl sulfotransferase separated from this bacterium differs from the sulfotransferase which uses 3'-phosphoadenosine 5'-phosphosulfate as a donor. The enzyme catalyzes stoichiometric transfer of a sulfate group from a phenol sulfate ester to other phenolic compounds, with strict specificity. The optimal pH and molecular weight were 8-9 and 315,000, respectively.     

Effect of Intracellular ATP Levels on the Light-Induced H+ Efflux from Intact Cells of Cyanidium caldarium

The light-induced H⁺ efflux observed at acidic pH in Cyanidiumcells was shown to be an active H⁺ transport depending on theintracellular ATP produced by cyclic photo-phosphorylation.Triton X-100 was found to act as an effective uncoupler in intactCyanidium cells without collapsing the pH gradient across theplasma membrane. Triton X-100 at 0.015% significantly reducedthe intracellular ATP levels, stimulated the p-BQ, Hill reactionand completely inhibited the light-induced H⁺ efflux. Inhibitionof the H⁺ efflux by Triton X-100 correlated well with the depressionof the apparent rale of light-induced ATP synthesis as wellas the decrease in the intracellular ATP level in light. The light-induced H⁺ efflux was completely inhibited by diethylstilbestrol,a specific inhibitor of plasma membrane ATPase, without anychanges in the intracellular ATP level, thereby suggesting theparticipation of the plasma membrane ATPase in the light-inducedH⁺ efflux. ¹The data in this paper are included in the Ph. D. dissertationsubmitted by M. Kura-Hotta to Tokyo Metropolitan University. (Received February 3, 1984; Accepted June 14, 1984)     

Immunological properties and ganglioside recognitions by Campylobacter jejuni-enterotoxin and cholera toxin

Abstract The immunological properties of Campylobacter jejuni enterotoxin (CJT) and cholera toxin (CT) were compared by enzyme-linked immunosorbent assay (ELISA) and Western blotting analysis with antiserum against each toxin. Antibody against CJT recognized the 68, 54 and 43 kDa polypeptides of CJT and the 11 kDa subunit of CT, whereas antibody against CT recognized the 68 and 54 kDa polypeptides of CJT and 11 kDa subunit of CT. The immunological reactions between the heterogenous combinations of toxins and the antibodies were weaker than those between the homogenous systems. Thus, different antigenicity was found in CJT and CT at the subunit level, although they possessed cross-reactive epitope(s). The binding of CJT and CT to gangliosides was also examined. CJT and CT bound to GM₁ ganglioside preferentially than to other ganglioside species. However, CJT did not bind to GD₁b in spite of the fact that CT preferred GD₁b. This suggests that both toxins recognize different receptors on the surface of the target cell. This study is the first demonstration of the different properties between CJT and CT in immunological character and ganglioside recognition.     

Localization of FMRFamide- and ACEP-1-like immunoreactivities in the nervous system and heart of a pulmonate mollusc,Achatina fulica

Immunohistochemical localization of two neuropeptides possibly involved in the regulation of cardiac activity in a pulmonate mollusc, Achatina fulica Férussac, was studied. On the ventral surface of the right cerebral ganglion, more than 50 neurons with diameters of 30–50 m showed immunoreactivity to the antiserum of the neuropeptide FMRFamide. Many were also immunoreactive to an antiserum raised against Achatina cardio-excitatory peptide-1 (ACEP-1). Although FMRFamidelike immunoreactive neurons occurred in all components of the subesophageal ganglia, identifiable ACEP-1-like immunoreactive neurons were located only in the visceral ganglion and the right parietal ganglion. In the heart, FMRFamide- and ACEP-1-like immunoreactive fibers were restricted to the atrium and the aortic end of the ventricle, consistent with morphological observations of cardiac innervation. The present results suggest that FMRFamide-and ACEP-1-like peptides are involved in regulating the heart beat of this snail.     

Incorporation of Very-Long-Chain Fatty Acids into Sphingolipids of Cultured Neural Cells

We examined effects of exogenous very-long-chain fatty acids on lipids of cultured chick neurons and astrocytes. When chick neurons were incubated in chemically defined medium containing 10 microM nervonic acid (C24:1) for 7 days, it was found that a major fatty acid moiety of gangliosides and sphingomyelin was nervonic acid itself, which was not normally detected in the sphingolipid fraction. This alteration in the fatty acid composition apparently occurred in each ganglioside species. Under these experimental conditions, nervonic acid was not found in the glycerophospholipid fraction, and the amounts of triacylglycerol and free nervonic acid increased. Addition of behenic acid (C22:0) or erucic acid (C22:1) also induced changes in the fatty acid composition of gangliosides. When chick astrocytes were incubated in the presence of 10 microM nervonic acid for 7 days, no significant change was observed in the fatty acid composition of gangliosides. These studies indicate that the manipulation of the fatty acid moiety of sphingolipids in cultured neurons is possible.