Nitric Oxide Reversibly Suppresses Xanthine Oxidase Activity

The effects of nitric oxide (NO) on xanthine oxidase (XOD) activity and the site(s) of the redox center(s) affected were investigated. XOD activity was determined by superoxide (O₂^-) generation and uric acid formation. NO reversibly and dose-dependently suppressed XOD activity in both determination methods. The suppression interval also disclosed a dose-dependent prolongation. The suppression occurred irrespective of the presence or absence of xanthine; indicating that the reaction product of NO and O₂^-, peroxynitrite, is not responsible for the suppression. Application of synthesized peroxynitrite did not affect XOD activity up to 2 μM. Methylene blue, which is an electron acceptor from Fe/S center, prevented the NO-induced inactivation. The results indicate that NO suppresses XOD activity through reversible alteration of the flavin prosthetic site.     

Enhanced production of rat interleukin-8 by in vitro and in vivo infections with influenza A NWS virus.

We investigated the interleukin-8 (IL-8)-producing activity of influenza A NWS virus in cultured rat kidney NRK-52E cells and a rat influenza model. The production of rat IL-8 increased significantly in the virus-infected cells but not in UV-inactivated virus- or split-product-treated cells. The increase in IL-8 production could be detected in the bronchoalveolar lavage of infected rats. These data suggest that infectious virus has the potential to accelerate the production of IL-8 in cultured cells and in vivo in airway-lining cells.     

Tissue-Specific Isoforms of Catalase Subunits in Castor Bean Seedlings

Catalases purified from endosperm glyoxysomes and non-specializedmicrobodies from hypocotyls of castor bean seedlings differedin their specific activity [90–164 and 0.89–4.9kunits (mg protein)^–1, respectively] and in their constituentsubunits [two subunits of 54 and 56 kDa for the endosperm enzymeand only one of 56 kDa for the hypocotyl enzyme]. Immunoblotanalysis also showed that particulate fractions from the endospermsand from etiolated and green cotyledons contained two catalasesubunits of 54 and 56 kDa, whereas such fractions from the hypocotylsand roots contained only the 56-kDa subunit. Leaf peroxisomesfrom green leaves had two catalase subunits of around 55 kDaeach. Results of translation in vitro indicated that the 54-and 56-kDa subunits were translated from distinct mRNAs andlevels of both mRNAs increased in the endosperms during germination,prior to increases in levels of catalase proteins. In the hypocotyls,the 56-kDa subunit seemed to be synthesized constitutively. ¹Present addresses: YO, Toyota Central Institute, 31-9 Musashizuka,Nagabuchi, Nagakute, Aichi 480-11, Japan     

Effects of detergents on the secondary structures of prion protein peptides as studied by CD spectroscopy.

Pathogenic prion proteins (PrP(Sc)) are thought to be produced by alpha-helical to beta-sheet conformational changes in the normal cellular prion proteins (PrP(C)) located solely in the caveolar compartments. In order to inquire into the possible conformational changes due to the influences of hydrophobic environments within caveolae, the secondary structures of prion protein peptides were studied in various kinds of detergents by CD spectra. The peptides studied were PrP(129-154) and PrP(192-213); the former is supposed to assume beta-sheets and the latter alpha-helices, in PrP(Sc). The secondary structure analyses for the CD spectra revealed that in buffer solutions, both PrP(129-154) and PrP(192-213) mainly adopted random-coils (approximately 60%), followed by beta-sheets (30%-40%). PrP(129-154) showed no changes in the secondary structures even in various kinds of detergents such as octyl-beta-D-glucopyranoside (OG), octy-beta-D-maltopyranoside (OM). sodium dodecyl sulfate (SDS), Zwittergent 3-14 (ZW) and dodecylphosphocholine (DPC). In contrast, PrP(192-213) changed its secondary structure depending on the concentration of the detergents. SDS, ZW, OG and OM increased the alpha-helical content, and decreased the beta-sheet and random-coil contents. DPC also increased the alpha-helical content, but to a lesser extent than did SDS, ZW, OG or OM. These results indicate that PrP(129-154) has a propensity to adopt predominantly beta-sheets. On the other hand, PrP(192-213) has a rather fickle propensity and varies its secondary structure depending on the environmental conditions. It is considered that the hydrophobic environments provided by these detergents may mimic those provided by gangliosides in caveolae, the head groups of which consist of oligosaccharide chains containing sialic acids. It is concluded that PrP(C) could be converted into a nascent PrP(Sc) having a transient PrP(Sc) like structureunder the hydrophobic environments produced by gangliosides.     

Analysis of the thromboxane/prostacyclin balance in human urine by gas chromatography/selected ion monitoring: abnormalities in diabetics

We microanalyzed 2,3-dinor-6-keto-prostaglandin F_1α (2,3-dinor-6-keto-PGF_1α 1) and 11-dehydrothromboxane B₂ (11-dehydro-TXB₂, 2) in human urine. Samples containing a [²H₄]-analogue as an internal standard were extracted by chromatography using Sep Pak tC18 and silica gel. The compounds were then analysed by means of the lactone ring opening reaction and dimethylisopropylsilylation. The conversion of 1 to 1-methyl ester (ME)-propylamide (PA)-9,12,15-dimethylisopropylsilyl (DMIPS) ether derivative and of 2 to 1-ME-6-methoxime (MO)-9,12,15-tris-DMIPS ether derivative was followed by gas chromatography/selected ion monitoring (GC/SIM). Interfering substances from the urine matrix were eliminated during GC/SIM analysis using a DB-5 column. We were able to detect 1 (222–1031 pg/mg creatinine) and 2 (18–155 pg/mg creatinine) in human urine. Furthermore, the thromboxane/prostacyclin (IX/PGI) ratio in the urine of diabetics was higher than that of healthy volunteers. This method can be used to determine the TX/PGI balance in human urine.     

Novel mutation at the initiation codon in the Norrie disease gene in two Japanese families

We have identified a new mutation of Norrie disease (ND) gene in two Japanese males from unrelated families; they showed typical ocular features of ND but no mental retardation or hearing impairment. A mutation was found in both patients at the initation codon of exon 2 of the ND gene (ATG to GTG), with otherwise normal nucleotide sequences. Their mothers had the normal and mutant types of the gene, which was expected for heterozygotes of the disease. The mutation of the initiation codon would cause the failure of ND gene expression or a defect in translation thereby truncating the amino terminus of ND protein. In view of the rarity and marked heterogeneity of mutations in the ND gene, the present apparently unrelated Japanese families who have lived in the same area for over two centuries presumably share the origin of the mutation.     

Novel preparation method for surfactant-coated enzymes using W/O emulsion

Summary A novel preparation method for surfactant-coated enzymes has been developed using a W/O emulsion. The enzymatic activity of chymotrypsin in isooctane significantly increased with the coating of surfactants. The surfactant-coated chymotrypsin showed a high enzymatic activity for amidation, although powdered chymotrypsin did not show the activity. Further, the coated enzyme showed a remarkably high storage stability.     

The effect of membrane preparation and cellular maturation on human erythrocyte adenylate cyclase

We found that adenylate cyclase activity of human erythrocytes is potentially labile during isolation of their plasmalemma. Addition of 1 mM EGTA to solution used to remove hemoglobin from lysed cells protected activity. Human erythrocyte adenylate cyclase is minimally activated by catecholamines, in the absence or presence of exogenous guanyl nucleotide, but substantially by 5′-guanylyl imidodiphosphate or sodium fluoride and concentration-dependently by Mg²⁺ or Mn²⁺. Basal catalytic activity is an age-dependent component of the human erythrocyte; 5′-guanylyl imidodiphosphate- or fluoride-activated activities decline with cellular maturation proportionally to the decrease in basal activity.     

Characterization of Nitrate Reductase from Corn Leaves (Zea mays cv W64A x W182E) : Two Molecular Forms of the Enzyme

The primary leaves from corn seedlings grown for 6 days were harvested, frozen with liquid N₂ and extracted in a Tris buffer (pH 8.5, 250 millimolar) containing 1 millimolar dithiothreitol, 10 millimolar cysteine, 1 millimolar EDTA, 20 micromolar flavin adenine dinucleotide and 10% (v/v) glycerol. Nitrate reductase (NR) in the crude extract was stable for several days at 0°C and for several months at −80°C. The enzyme was purified using (NH₄)₂SO₄ fractionation, brushite-hydroxyl-apatite chromatography and blue-sepharose affinity chromatography. The enzyme was eluted from the blue-sepharose column with a linear gradient of NADH (0-100 micromolar) or with 0.3 molar KNO₃. About 10% of the original activity was recovered with NADH (NADH-NR). It had a specific activity of about 60 to 70 units (micromoles NO₂⁻ per minute per milligram protein). A sequential elution with NADH followed by KNO₃ (0.3 molar) or KCl (0.3 molar) yielded 2 peaks. Rechromatography of each peak gave two peaks again. These results indicate that we are dealing with two forms of the same enzyme rather than two different NR proteins. The two NRs had different molecular weights as judged by chromatography on Toyopearl. The NADH-NR was more sensitive than the NO₃⁻-NR to antibody prepared against barley leaf NR. In Ouchterlony assays a single precipitin line, with completely fused boundaries, was observed.