Identification of NAD(P)H Quinone Oxidoreductase Activity in Azoreductases from P. aeruginosa: Azoreductases and NAD(P)H Quinone Oxidoreductases Belong to the Same FMN-Dependent Superfamily of Enzymes

Water soluble quinones are a group of cytotoxic anti-bacterial compounds that are secreted by many species of plants, invertebrates, fungi and bacteria. Studies in a number of species have shown the importance of quinones in response to pathogenic bacteria of the genus Pseudomonas. Two electron reduction is an important mechanism of quinone detoxification as it generates the less toxic quinol. In most organisms this reaction is carried out by a group of flavoenzymes known as NAD(P)H quinone oxidoreductases. Azoreductases have previously been separate from this group, however using azoreductases from Pseudomonas aeruginosa we show that they can rapidly reduce quinones. Azoreductases from the same organism are also shown to have distinct substrate specificity profiles allowing them to reduce a wide range of quinones. The azoreductase family is also shown to be more extensive than originally thought, due to the large sequence divergence amongst its members. As both NAD(P)H quinone oxidoreductases and azoreductases have related reaction mechanisms it is proposed that they form an enzyme superfamily. The ubiquitous and diverse nature of azoreductases alongside their broad substrate specificity, indicates they play a wide role in cellular survival under adverse conditions

Insights into technetium amidoxime complex: oxo technetium(V) complex of n-substituted benzamidoxime as new basic structure for molecular imaging

In search of benzamidoxime (BHam) derivatives that provide a single 99mTc-labeled compound of high in vivo stability, we synthesized three N-alkyl compounds of benzamidoxime (BHam) ligand. They provided a single 99mTc-labeled compound by ligand exchange reaction of 99mTc-glucoheptonate in high radiochemical yields (over 95% at MBHam concentration of 1 × 10−5 M). 99mTc-N-methyl benzamidoxime (99mTc-MBHam) showed higher stability than the parental 99mTc-BHam. The complex of this compound with 99gTcO3+ ion was prepared, isolated, and characterized by FT-IR and NMR spectra as well as X-ray diffraction. 99gTc-MBHam crystallized in an orthorhombic space group Pna21 with a = 13.4823(5), b = 15.5410(7), c = 7.7907(3) Å, V = 1632.39(11) Å3, and Z = 4. The 99gTc complex possessed square base pyramid coordination geometry. The equatorial plane was formed by two-amine nitrogen and two-oxime oxygen atoms in trans position, while the oxo core of the technetium(V) occupied the apical position. The 99gTc-MBHam proved to be identical with the 99mTc-MBHam prepared at the no-carrier-added level by comparison of their HPLC profiles