p-aminobenzoate N-oxygenase (AurF) from Streptomyces thioluteus catalyzes the formation of unusual polyketide synthase starter unit p-nitrobenzoic acid (pNBA) from p-aminobenzoic acid (pABA) in the biosynthesis of antibiotic aureothin. AurF is a metalloenzyme, but its native enzymatic activity has not been demonstrated in vitro, and its catalytic mechanism is unclear. In addition, the nature of the cofactor remains a controversy. Here, we report the in vitro reconstitution of the AurF enzyme activity, the crystal structure of AurF in the oxidized state, and the cocrystal structure of AurF with its product pNBA. Our combined biochemical and structural analysis unequivocally indicates that AurF is a non-heme di-iron monooxygenase that catalyzes sequential oxidation of aminoarenes to nitroarenes via hydroxylamine and nitroso intermediates.di-iron enzymes ͉ metalloenzymes ͉ N-oxygenation ͉ reaction mechanism

Background-The risks and benefits of long-term dual antiplatelet therapy remain unclear. Methods and Results-This prospective, multicenter, open-label, randomized comparison trial was conducted in 24 clinicalcenters in Korea. In total, 5045 patients who received drug-eluting stents and were free of major adverse cardiovascular events and major bleeding for at least 12 months after stent placement were enrolled between July 2007 and July 2011.Patients were randomized to receive aspirin alone (n=2514) or clopidogrel plus aspirin (n=2531 Continuing medical education (CME) credit is available for this article. Go to http://cme.ahajournals.org to take the quiz.