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Notes: Specific inhibitors of the membrane-bound dipeptidyl peptidase IV (DP IV) and polyclonal antibodies against this enzyme were used to investigate the relationships between DP IV activity and the production and action of T cell-derived lymphokines. Production of interleukin 2 (IL-2) and gamma interferon by mitogen plus phorbol ester-simulated mononuclear cells Bran human blood was found to be reduced in the presence of N-Ala-Pro-O-(nitrobenzoyl-)-hydroxylamine, epsilon-(4′nitro) benzoxycarbonyl-Lys-Pro, and anti-(DP IV) immunoglobulin in a dose-dependent manner. Moreover, the proliferative response of mitogen-stimulated mononuclear cells to IL-2 is impaired in the presence of DP IV inhibitors. Therefore it is suggested that the membrane peptidase DP IV is involved in the induction and activation of cytokines controlling lymphocyte proliferation

Notes: Summary The suitability of Z-Arg-Gly-Phe-Phe-Leu-MNA and Z-Arg-Gly-Phe-Phe-Pro-MNA for the assessment of cathepsin D activity was tested in biochemical and histochemical experiments. Substrates were dissolved in dimethylformamide and used at 0.1–0.5 mM in various buffers over a pH range of 3.5–7.4. Homogenates of various rat organs and isolated purified enzymes [cathepsin D from bovine spleen, dipeptidyl peptidase (DPP) I.V from porcine kidney and rat lung] were used as enzyme sources. Pepstatin, di-isopropylfluorophosphate (DFP),p-chloromercuribenzoate,o-phenanthroline and a series of DPP IV inhibitors were used in inhibitor experiments. At pH 3.5 and 5.0, substrates were used in a two-step postcoupling procedure with aminopeptidase M and dipeptidyl peptidase IV as auxiliary enzymes and Fast Blue BB as coupling agent. Results were compared with those obtained with haemoglobin. Above pH 5.0 substrates were used in a one-step postcoupling procedure. Cryostat sections of snap-frozen or cold aldehyde-fixed tissue pieces of various rat organs and biopsies of human jejunal mucosa were used in histochemical experiments. As in biochemical tests a two-step procedure was used in the pH range 3.5–5.0, but Fast Blue B was used in the second step for the simultancous coupling. Above pH 5.0 a onestep simultaneous azo coupling procedure was used with Fast Blue B as coupling agent. At pH 3.5 the hydrolysis rate of both synthetic substrates was about 100 x lower than that of haemoglobin when cathepsin D from bovine spleen was used. The activity was inhibited by pepstatin. With increasing pH the hydrolysis rate of Z-Arg-Gly-Phe-Phe-Pro-MNA increased, while that of Z-Arg-Gly-Phe-Phe-Leu-MNA decreased when organ homogenates were used as enzyme sources. However, the activity was not inhibited by pepstatin. It was inhibited by DFP. The extent of the inhibition with other substances was species and organ dependent. Z-Arg-Gly-Phe-Phe-Pro-MNA was also cleaved by isolated and purified DPP IV of porcine kidney and rat lung and the activity was inhibited by DFP and DPP IV inhibitors. In histochemical experiments the staining obtained with both synthetic substrates at pH 3.5 was weak and rather diffuse, with only slight accentuation or none at all in the lysosomal region of cells. In the pH range 5.5–7.4 a very distinct reaction was observed with Z-Arg-Gly-Phe-Phe-Pro-MNA only. The reaction product was localized in the brush border of enterocytes and of cells of the proximal kidney tubules. Endothelial cells of glomeruli and capillaries of the propria of the human jejunum also displayed a positive reaction. Lymphocytes in the propria of rat small intestine reacted to some extent. The reaction was inhibited by DFP. The extent of the inhibition with other substances varied. Z-Arg-Gly-Phe-Phe-Leu-MNA and Z-Arg-Gly-Phe-Phe-Pro-MNA are not efficient substrates for the assessment of cathepsin D activity. In histochemical studies diffusion artifacts must always be considered. In the pH range 5.5–7.4, Z-Arg-Gly-Phe-Phe-Pro-MNA is cleaved by a serine endopeptidase and by a metalloendopeptidase. It remains to be established whether prolyl endopeptidase or DPP IV (or both) and which metalloendopeptidase are responsible for the cleavage. In the evaluation of enterobiopsies the demonstration of this activity is a sensitive means for the assessment of the state of the brush border.

Notes: Abstract Nickel and ammonium ion exchanged NaY zeolites have been investigated in dimerization of n-butenes in the liquid phase. The dimerization reaction proceeds by a coordinative as well as carbenium ion reaction mechanism.

Notes: Die Reduzierbarkeit des Ni2+ in X- und Y-Zeolithen durch Wasserstoff, But-l-en, Propen und Ethen wird verglichen. Der Reduktionsgrad wurde nach isothermer Reduktion und Reoxydation durch temperaturprogrammierte Reduktion bestimmt. Für die Reduzierbarkeit bei 673 K ergibt sich für einen X-Zeolith folgende Reihenfolge: H2 〉 But-l-en, Propen 〉 Ethen. Am Y-Zeolith erfolgt eine Umkehrung: But-l-en, Propen 〉 H2, Ethen. Der Mechanismus der Reduktion durch Olefine sollte durch einen sauer katalysierten Olefinzerfall mit intermediärer H- -Abspaltung als reduzierendem Agenz bestimmt sein. Ein solcher Mechanismus erklärt die stärkere Reduktion des Ni2+ in Y-Zeolithen durch Olefine. Nimmt man als aktives Zentrum für die Ethendimerisierung niedrigwertiges Nickel an, so wird die bei der Ethendimerisierung auftretende Induktionsperiode durch die notwendige Reduktion des Ni2+ erklärbar.

Notes: Die Struktur der TPR-Kurven verschieden ausgetauschter NiNaX-und NiNaY-Zeolithe wird durch die unterschiedliche Kationenverteilung bestimmt. Bei X-Zeolithen erscheint ein Tieftemperturpeak mit einem Maximum im Bereich 750-800K und für höhere Austauschgrade zusätzlich ein Hochtemperaturpeak bei etwa 1000 K (Reduktion von Ni2+ suf SII- und SI′- bzw. SI-Positionen). Bei Y-Zeolithen Können drei Reduktionsbereiche (Reduction auf SII, SI und SI) unterschieden werden. Das Maximum des Hochtemperaturpeaks verschiebt sich mit steigendem Si/Al-Verhältnis zo höheren Temperaturen. Dei Reduzierbarkeit im Bereich niedrigerer Temperaturen ist für X-Zeolithe größer,dei bei Reduktion bis zo hohen Temperaturen erreichbaren Reduktionsgrade liegen für Y-Zeolithe höher. Die kinetische Analyse ergab für den Tieftemperaturpeak je nach der gewählten Methode (85 ± 10) bzw. (86 ± 2) kJ/mol Aktivierungsenergie, für den Hochtemperaturpeak (223 ± 12) bzw. (214 ± 2) kJ/mol.