N-Hydroxyguanidine Compound 1-(3,4-Dimethoxy- 2-chlorobenzylideneamino)-3-hydroxyguanidine Inhibits the Xanthine Oxidase Mediated Generation of Superoxide Radical

• Published in: Archives of biochemistry and biophysics Vol. 377; no. 1; pp. 101 - 108
• Main Authors: Dambrova, Maija, Baumane, Larisa, Kiuru, Anne, Kalvinsh, Ivars, Wikberg, Jarl E.S.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.05.2000
• Subjects: allopurinol; Allopurinol - metabolism; Allopurinol - pharmacology; Animals; Binding Sites - drug effects; Catalysis - drug effects; Cattle; Chromatography, High Pressure Liquid; Electron Spin Resonance Spectroscopy; EPR; Guanidines - metabolism; Guanidines - pharmacology; Guanidines - therapeutic use; inhibitor; Inhibitory Concentration 50; Kinetics; Milk - enzymology; Models, Chemical; Molybdenum - metabolism; N-hydroxyguanidine derivative; NAD - metabolism; Onium Compounds - metabolism; Onium Compounds - pharmacology; Oxidation-Reduction - drug effects; Oxygen - metabolism; Reperfusion Injury - drug therapy; superoxide; Superoxides - metabolism; Uric Acid - metabolism; Xanthine - metabolism; xanthine oxidase; Xanthine Oxidase - antagonists & inhibitors; Xanthine Oxidase - metabolism; inhibitor; superoxide; allopurinol; xanthine oxidase; EPR; N-hydroxyguanidine derivative
• ISSN: 0003-9861; 1096-0384
• DOI: 10.1006/abbi.2000.1745

We here show that the novel N-hydroxyguanidine derivative PR5 (1-(3,4-dimethoxy-2-chlorobenzylideneamino)-3-hydroxyguanidine) is acting as an alternative electron acceptor in xanthine oxidase catalyzed oxidation of xanthine. The reduction product is the corresponding guanidine derivative 1-(3,4-dimethoxy-2-chlorobenzylideneamino)guanidine (PR9). The reaction occurs under both anaerobic and aerobic conditions. Moreover, EPR measurements show that the action of PR5 is associated with the inhibition of superoxide radical formation seen under aerobic conditions. PR5 also supports xanthine oxidase catalyzed anaerobic oxidation of NADH. Kinetic studies indicate that increasing xanthine concentration significantly increases the apparent Km of PR5, but it remains unaltered by changing NADH concentration. Moreover, the molybdenum center inhibitor allopurinol inhibits the PR5-sustained oxidation of xanthine and NADH equally well, whereas the flavin adenine dinucleotide site inhibitor diphenyliodonium (DPI) markedly inhibits only the PR5-sustained oxidation of NADH. We suggest that PR5 binds and becomes reduced at the molybdenum center of the xanthine oxidase. We also found that both PR5 and its reduction product PR9 can inhibit the oxygen-sustained xanthine oxidase reaction. The properties of PR5 suggest that it is a member of a novel class of compounds which we have termed xanthine oxidase electron acceptor–inhibitor drugs. The potential use of xanthine oxidase electron acceptor–inhibitors in the prevention of free radical mediated tissue damage in organ ischemia–reperfusion diseases is discussed.