The full-length, protein coding sequence for dehaloperoxidase was obtained using a reverse genetic approach and a cDNA library from marine worm Amphitrite ornata. The crystal structure of the dehaloperoxidase (DHP) was determined by the multiple isomorphous replacement method and was refined at 1.8-Å resolution. The enzyme fold is that of the globin family and, together with the amino acid sequence information, indicates that the enzyme evolved from an ancient oxygen carrier. The peroxidase activity of DHP arose mainly through changes in the positions of the proximal and distal histidines relative to those seen in globins. The structure of a complex of DHP with 4-iodophenol is also reported, and it shows that in contrast to larger heme peroxidases DHP binds organic substrates in the distal cavity. The binding is facilitated by the histidine swinging in and out of the cavity. The modeled position of the oxygen atom bound to the heme suggests that the enzymatic reaction proceeds via direct attack of the oxygen atom on the carbon atom bound to the halogen atom.Polychlorinated phenols and other polychlorinated aromatics of anthropogenic origin have been widely dispersed and constitute significant environmental problems. It is less known that bromoaromatics of biotic origin are also widespread and secreted as chemical warfare by a number of marine organisms. Dehalogenating enzymes are used as the first line of defense against these toxicants by organisms that live in such contaminated environments (1). We have recently discovered and characterized by a number of techniques (2-4) an enzyme with a novel function, dehaloperoxidase (DHP).1 DHP is isolated from Amphitrite ornata, a terebellid polychaete. This species does not produce halogenated compounds itself but usually co-habits estuarine mud flats with other polychaete worms, such as Notomastus lobatus, and hemichordata such as Saccoglossus kowalewskyi, which secrete large quantities of brominated aromatics and other halometabolites as repellents (5). The levels of DHP are very high as it represents approximately 3% of the soluble protein in crude extracts of A. ornata. The enzyme catalyzes the oxidative dehalogenation of polyhalogenated phenols in the presence of hydrogen peroxide at a rate at least 10 times faster than all known halohydrolases of bacterial origin, according to Reaction 1.The oxidative potential of hydrogen peroxide likely allows for the unusually high rate of this reaction as well as for the unique ability of DHP to dehalogenate fluorophenols. The enzyme has activity toward substrates with different numbers and positions of halogen substituents (2).The binding of oxygen and peroxide ligands and their activation are due to the presence of heme in a variety of oxygen carriers and enzymes. This is also true for DHP, which contains one heme per subunit (3) and a histidine as the proximal iron ligand (4). The propensity of peroxidases (and oxygenases, which tend to have a cysteinate proximal ligand) to cleave the oxygen-oxygen bond and form a high vale...

Bacteria are now becoming more resistant to most conventional antibiotics. Methicillin-resistant Staphylococcus aureus (MRSA), a complex of multidrug-resistant Gram-positive bacterial strains, has proven especially problematic in both hospital and community settings by deactivating conventional β-lactam antibiotics, including penicillins, cephalosporins, and carbapenems, through various mechanisms, resulting in increased mortality rates and hospitalization costs. Here we introduce a class of charged metallopolymers that exhibit synergistic effects against MRSA by efficiently inhibiting activity of β-lactamase and effectively lysing bacterial cells. Various conventional β-lactam antibiotics, including penicillin-G, amoxicillin, ampicillin, and cefazolin, are protected from β-lactamase hydrolysis via the formation of unique ion-pairs between their carboxylate anions and cationic cobaltocenium moieties. These discoveries could provide a new pathway for designing macromolecular scaffolds to regenerate vitality of conventional antibiotics to kill multidrug-resistant bacteria and superbugs.

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The terebellid polychaete Amphitrite ornata produces no detectable volatile halogenated secondary metabolites, but frequently inhabits coastal marine sediments heavily contaminated with anthropogenic or biogenic haloaromatic compounds. This animal contains high levels of two very unusual enzymes, dehalogenating peroxidases. We have purified and partially characterized one of these dehaloperoxidases, DHP I. DHP I is a heme enzyme (M r ‫؍‬ 30,790) composed of two identical subunits (M r ‫؍‬ 15,529) and is very rich in the amino acids aspartic acid (؉ asparagine) and glutamic acid (؉ glutamine). The enzyme converts trihalogenated phenols, such as 2,4,6-tribromophenol, into dihalogenated quinones. The optimum pH for this reaction is 5.0. DHP I is also active against di-and monohalogenated phenols and will oxidize bromo-, chloro-, and fluorophenols. We have identified similar dehaloperoxidase activities in other infaunal polychaetes, including halometaboliteproducing species.

We report novel robust resin acid-derived antimicrobial agents that exhibit excellent antimicrobial activities against a broad spectrum of bacteria (6 Gram-positive and 7 Gram-negative) with selective lysis of microbial membranes over mammalian membranes. Our results indicate that hydrophobicity and unique structures of resin acids can be determining factors in dictating the antimicrobial activity.