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.     

Cell-Free Synthesis of a Putative Precursor of Polygalacturonase in Tomato Fruits

By using a monospecific anti-polygalacturonase-2 antibody, a54K-dalton polypeptide was detected in in vitro translationproducts by a wheat germ cell-free translation system programmedwith polyadenylated RNA from ripe tomato pericarp tissue. Thisputative precursor of polygalacturonase was about 9K daltonslarger in molecular weight than polygalacturonase-2. (Received December 12, 1983; Accepted May 17, 1984)     

The presence of partially degraded collagen fragments in the resorbing granulation tissue in rats.

Insoluble collagen of granulation tissue produced by carrageenin injection was solubilized by pepsin treatment and purified. The pepsin-solubilized insoluble collagen contained partially degraded collagen fragments and the amounts of these small fragments of collagen were much greater in the resorbing granulation tissues than in the growing tissues, suggesting that these small fragment were formed in the course of resorption of granulation tissue, including collagen breakdown.     

IgE-mediated 14C-serotonin release from rat mast cells modulated by morphine and endorphins

The formaldehyde method was used to examine the interaction of PGE₁ with morphine, β-endorphin and Met-enkephalin on rat mast cells by their effects on IgE-mediated ¹⁴C-serotonin release. PGE₁ (2×10^?8?2×10^?5 M) caused a dose-related inhibition of the mediator release 1 min after an antigen challenge, and morphine (3×10^?7?3×10^?5 M) reversed this PGE₁ effect dose-dependently and stereospecifically; naloxone (2×10^?4 M) antagonized this action of morphine. β-Endorphin (3×10^?7?10^?5 M) and Met-enkephalin (3×10^?6?10^?4 M) mimicked this morphine action dose-dependently and were antagonized by naloxone (2×10^?4 M). These results suggest that morphine and endorphins modulate immunological mediator release from rat mast cells through opioid receptors.     

Induction of proliferation and Ig production in human B leukemic cells by anti-immunoglobulins and T cell factors

The proliferation and differentiation of human leukemic B cells (B-CLL cells) with anti-Ig and T cell-derived helper factors are described. Stimulation of B-CLL cells with anti-Ig and T helper factors could induce proliferation as well as differentiation into IgM- and IgG-producing cells. Neither anti-Ig nor T helper factors alone could induce any proliferation and/or differentiation of B-CLL cells. Not only whole molecules of anti-Ig but also F(ab')2 fragments could induce proliferation and differentiation of B-CLL cells in the presence of T helper factors, but monovalent Fab' fragments were not effective. Induction of both IgM and IgG with the same idiotype was confirmed by immunofluorescent and SDS-PAGE analysis. By employing an IL 2-dependent cytotoxic T cell line and a TRF-responsive B cell line, T cell factors were separated into a fraction with IL2 activity but no TRF activity and a fraction with TRF activity but no IL 2 activity by chromatofocusing. Anti-Ig and IL 2 fraction could induce proliferation of B-CLL cells, but TRF fraction was not effective for the induction of proliferation in anti-IG-stimulated cells. For IgM and IgG production, anti-Ig and both IL 2 and TRF fractions were required. Depletion of IL 2 fraction in the first 2 days' culture inhibited Ig production, whereas the absence of TRF fraction in the first 2 days did not show any inhibitory effect on Ig production.     

Inactivation of dioldehydrase in the presence of a coenzyme-B12 analog

We have previously shown that a coenzyme-B₁₂ analog, adenosylcobalamin (AdoCbl)-(e-OH), with the e-propionamide group converted to a carboxylic acid, serves as a poor coenzyme for dioldehydrase. During the course of the catalytic process, the enzyme AdoCbl-(e-OH) complex becomes catalytically inactive (T. Toraya, E. Krodel, A. S. Mildvan, and R. H. Abeles, 1979, Biochemistry18, 417–426). We have now examined the mechanism of this inactivation further. Inactivation only occurs in the presence of substrate. The dioldehydrase coenzyme analog complex is stable in the absence of substrate. In the inactivated complex, the coenzyme analog was stoichiometrically converted to a cob(II)alamin species. The cob-(II)alamin formed remained irreversibly bound at the active site of the enzyme and resisted oxidation by O₂ even in the presence of CN^?. Stoichiometric formation of 5′-deoxyadenosine from the 5′-deoxy-5′-adenosyl moiety of the coenzyme analog was demonstrated with [8-¹⁴C]-AdoCbl(e-OH). This nucleoside also remained tightly bound to the enzyme and was not exchangeable with free 5′-deoxyadenosine nor was it removed by Sephadex chromatography. The rate of inactivation showed no deuterium isotope effect when the inactivation occurred in the presence of l,2-propanediol-l-d₂. The inactivated complex was resolved by acid ammonium sulfate treatment into the intact apoenzyme and the hydroxocobalamin derivative. This indicates that the apoenzyme itself is not modified in the inactivation process. These results suggest that the inactivation reaction occurs from one of the intermediates in the normal catalysis. We propose that the inactivation is due to incorrect binding of the modified coenzyme in an intermediate of the catalytic process. This incorrect binding leads to the loss of the substrate radical, and consequently, to loss of catalytic activity.     

Coenzyme B12-dependent diol dehydrase: Chemical modification with 2,3-butanedione and phenylglyoxal

The apoenzyme of diol dehydrase was inactivated by two arginine-specific reagents, 2,3-butanedione and phenylglyoxal, in borate buffer. In both cases, the inactivation followed pseudo-first-order kinetics. Kinetic data show that the incorporation of a single reagent molecule per active site of the enzyme is necessary for the complete inactivation. The modification with 2,3-butanedione was reversed by dilution of the reagent and borate concentrations (65% activity recovered). 1,2-Propanediol (substrate) partially protected the enzyme against inactivation. The holoenzyme was almost insensitive to 2,3-butanedione and phenylglyoxal, indicating that the essential arginine residue is prevented from the attack of these reagents either by direct blockage with the bound coenzyme or by an indirect conformational change caused by coenzyme binding. The inactivation of diol dehydrase by 2,3-butanedione did not result in dissociation of the enzyme into subunits. From these results, we concluded that the essential arginine residue is located at or in close proximity to the active site of diol dehydrase.     

Pathological observation on experimental swine dysentery

Experimental swine dysentery caused by 4 cultured strains (S73/2, DJ183, DJ70 and DK762) of Treponema hyodysenteriae was studied pathologically. The distribution and quantity of treponemes were examined on tissue sections stained by the Warthin-Starry method. Of the organs the colon contained the largest number of treponemes and the cecum and rectum the second largest number. Histopathological lesions were restricted to the large intestine. They ranged from mild catarrhal colitis in the mild case to desquamative, hemorrhagic colitis in the severest case. The severity of lesion was closely associated with the quantity of treponemes present. There was no difference in quality of the lesion between any two of the strains used in this study. Electron microscope revealed a large number of free treponemes present in the intestinal lumen and crypts. Treponemes were seen more frequently in the cytoplasm of goblet cells than in that of intestinal epithelial cells. They were also observed in desquamated degenerative epithelia. A small number of them were found in intact epithelia. Morphologically, the treponeme had a granular protoplasmic cylinder at the center which was surrounded by a thin envelope. Between the cylinder and the envelope there were axial fibrils.     

Stereoselective hydrolysis of dl-menthyl succinate by gel-entrapped Rhodotorula minuta var. texensis cells in organic solvent

Summary dl-Menthyl succinate was successfully hydrolyzed stereoselectively by Rhodotorula minuta var. texensis cells entrapped within photo-crosslinked or polyurethane resin gels in water-saturated n-heptane. The hydrolyzed product was found to be pure l-menthol. The catalytic activity of the immobilized cells, especially those entrapped in urethane polymers, was far more stable than that of the free cells. The half-life of the polyurethaneentrapped cells was estimated to be 55–63 days in the organic solvent.Dedicated to the 65th birthday od Professor Dr. G. Manecke     

Radioimmunoassay of ursodeoxycholic acid in serum

A sensitivie and specific radioimmunoassay for the measurement of serum ursodeoxycholic acid has been developed. Ursodeoxycholic acid bound to bovine serum albumin was used as an antigen, and antiserum to this antigen was raised in the rabbit. [11, 12-3h2]Ursodeoxycholic acid was used as the radioactive tracer, and the radioimmunoassay was carried out by the method of Simmonds et al. (1973. Gastroenterology. 65: 705-711). The percentage of bound radioactivity decreased linearly with a logarithmic increase in unlabeled ursodeoxycholic acid from 10 to 200 pmol. The antiserum showed extremely high specificity for ursodeoxycholic acid (free and conjugated), and the values determined by radioimmunoassay indicated a close correlation with those found by gas-liquid chromatography. In normal Japanese subjects, a small amount of ursodeoxycholic acid in serum was detected, and the level was detected, and the level was 0.15 +/- 0.11 nmol/ml. This convenient radioimmunoassay will provide useful information about the metabolism of ursodeoxycholic acid in man.