Publications

• Structure and function of arginases.

  Ash D.E.

  The arginases catalyze the divalent cation dependent hydrolysis of L-arginine to produce L-ornithine and urea. Although traditionally considered in terms of its role as the final enzyme of the urea cycle, the enzyme is found in a variety of nonhepatic tissues. These findings suggest that the enzym ... >> More

  The arginases catalyze the divalent cation dependent hydrolysis of L-arginine to produce L-ornithine and urea. Although traditionally considered in terms of its role as the final enzyme of the urea cycle, the enzyme is found in a variety of nonhepatic tissues. These findings suggest that the enzyme may have other functions in addition to its role in nitrogen metabolism. High-resolution crystal structures have been determined for recombinant rat liver (type I) arginase and for recombinant human kidney (type II) arginase, their variants, and complexes with products and inhibitors. Each identical subunit of the trimeric enzyme contains an active site that lies at the bottom of a 15 A deep cleft. The 2 essential Mn(II) ions are located at the bottom of this cleft, separated by approximately 3.3 A and bridged by oxygens derived from 2 aspartic acid residues and a solvent-derived hydroxide. This metal bridging hydroxide is proposed to be the nucleophile that attacks the guanidinium carbon of substrate arginine. On the basis of this proposed mechanism, boronic acid inhibitors of the enzyme have been synthesized and characterized kinetically and structurally. These inhibitors display slow-onset inhibition at the pH optimum of the enzyme, and are found as tetrahedral species at the active site, as determined by X-ray diffraction. The potent inhibition of arginases I and II by these compounds has not only delineated key enzyme-substrate interactions, but has also led to a greater understanding of the role of arginase in nonhepatic tissues. << Less

  J Nutr 134:2760S-2764S(2004) [PubMed] [EuropePMC]

• Structure of a unique binuclear manganese cluster in arginase.

  Kanyo Z.F., Scolnick L.R., Ash D.E., Christianson D.W.

  Each individual excretes roughly 10 kg of urea per year, as a result of the hydrolysis of arginine in the final cytosolic step of the urea cycle. This reaction allows the disposal of nitrogenous waste from protein catabolism, and is catalysed by the liver arginase enzyme. In other tissues that lac ... >> More

  Each individual excretes roughly 10 kg of urea per year, as a result of the hydrolysis of arginine in the final cytosolic step of the urea cycle. This reaction allows the disposal of nitrogenous waste from protein catabolism, and is catalysed by the liver arginase enzyme. In other tissues that lack a complete urea cycle, arginase regulates cellular arginine and ornithine concentrations for biosynthetic reactions, including nitric oxide synthesis: in the macrophage, arginase activity is reciprocally coordinated with that of NO synthase to modulate NO-dependent cytotoxicity. The bioinorganic chemistry of arginase is particularly rich because this enzyme is one of very few that specifically requires a spin-coupled Mn2+-Mn2+ cluster for catalytic activity in vitro and in vivo. The 2.1 angstrom-resolution crystal structure of trimeric rat liver arginase reveals that this unique metal cluster resides at the bottom of an active-site cleft that is 15 angstroms deep. Analysis of the structure indicates that arginine hydrolysis is achieved by a metal-activated solvent molecule which symmetrically bridges the two Mn2+ ions. << Less

  Nature 383:554-557(1996) [PubMed] [EuropePMC]

• Arginase: structure, mechanism, and physiological role in male and female sexual arousal.

  Christianson D.W.

  Mammalian arginases I and II require an intact binuclear manganese cluster for the hydrolysis of L-arginine to generate L-ornithine and urea. Although arginase isozymes differ in terms of their tissue distribution, cellular localization, and metabolic function, each employs a metal-activated hydro ... >> More

  Mammalian arginases I and II require an intact binuclear manganese cluster for the hydrolysis of L-arginine to generate L-ornithine and urea. Although arginase isozymes differ in terms of their tissue distribution, cellular localization, and metabolic function, each employs a metal-activated hydroxide mechanism for catalysis. To date, the best arginase inhibitors are those bearing N-hydroxyguanidinium or boronic acid "warheads" that can bridge the binuclear manganese cluster. Strikingly, the trigonal planar boronic acids undergo nucleophilic attack by hydroxide ion to form tetrahedral boronate anions that mimic the tetrahedral intermediate and its flanking transition states in the arginase mechanism. Given their affinity and specificity for arginase, boronic acid inhibitors are especially useful for probing the role of arginase in living systems. Arginase can regulate L-arginine bioavailability to nitric oxide synthase by depleting the substrate pool for NO biosynthesis, so arginase inhibition can enhance the substrate pool for NO biosynthesis. Accordingly, arginase inhibition can enhance NO-dependent physiological processes, such as the smooth muscle relaxation required for sexual arousal: administration of arginase inhibitors in vitro and in vivo enhances erectile function and engorgement in the male and female genitalia. Therefore, arginase is a potential therapeutic target for the treatment of sexual arousal disorders in men and women. << Less

  Acc Chem Res 38:191-201(2005) [PubMed] [EuropePMC]

• Arginase: a binuclear manganese metalloenzyme.

  Ash D.E., Cox J.D., Christianson D.W.

  Met Ions Biol Syst 37:407-428(2000) [PubMed] [EuropePMC]