Abstract
Rat liver arginase contains a dinuclear Mn2(II,II) center in each subunit having EPR properties similar to those observed in Mn-catalases. The principal physiologic role of arginase is catalyzing the hydrolytic cleavage of L-arginine to produce L-ornithine and urea. Here we demonstrate that arginase catalyzes the disproportionation of hydrogen peroxide by a redox mechanism analogous to Mn-catalases, but at rates that are 10-5 to 10-6 of k(cat) for the Mn-catalases, and also exhibits peroxidase activity. The dinuclear Mn2(II,II) center is essential for maximal catalase activity, since both the H101N and H126N mutant arginases containing only one Mn(II)/subunit have catalase activities that are <3% of that for the wild- type enzyme. Like the Mn-catalases, the catalase activity of arginase is not inhibited by millimolar concentrations of CN-, the most potent inhibitor of heme catalases, or by EDTA, a chelator of free metal ions. The catalase activity of arginase is not significantly inhibited by C1- or F-, in contrast to Mn-catalases, while potent inhibitors of the hydrolytic activity are also effective inhibitors of the catalase activity. These results suggest that lower affinity of hydrogen peroxide to the active site of arginase contributes to the lower catalase activity. EPR spectroscopy reveals that potent inhibitors of the hydrolytic reaction, including N(ω)-hydroxy-L- arginine, L-lysine, and L-valine, decouple the electronic interaction between the Mn2+ ions, most probably by removing a μ-bridging ligand or by increasing the intermanganese separation. The capacity for arginase to deliver a hydroxide ion to hydrolyze the L-arginine substrate is suggested to arise from a 'dinuclear effect', wherein the two metal ions contribute more or less equivalently in deprotonation of metal-bound water molecule. Structure-reactivity analyses of these reactions will provide insights into the factors that control redox versus hydrolytic function in dimanganese clusters.
| Original language | English |
|---|---|
| Pages (from-to) | 433-443 |
| Number of pages | 11 |
| Journal | Journal of Biological Inorganic Chemistry |
| Volume | 2 |
| Issue number | 4 |
| DOIs | |
| Publication status | Published - Aug 1997 |
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Keywords
- Arginase
- Catalase
- Manganoenzymes
- Peroxidase
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Biochemistry
Cite this
Catalysis on dinuclear Mn(II) centers : Hydrolytic and redox activities of rat liver arginase. / Sossong, Thomas M.; Khangulov, Sergei V.; Cavalli, R. Christopher; Soprano, Dianne Robert; Dismukes, G Charles; Ash, David E.
In: Journal of Biological Inorganic Chemistry, Vol. 2, No. 4, 08.1997, p. 433-443.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Catalysis on dinuclear Mn(II) centers
T2 - Hydrolytic and redox activities of rat liver arginase
AU - Sossong, Thomas M.
AU - Khangulov, Sergei V.
AU - Cavalli, R. Christopher
AU - Soprano, Dianne Robert
AU - Dismukes, G Charles
AU - Ash, David E.
PY - 1997/8
Y1 - 1997/8
N2 - Rat liver arginase contains a dinuclear Mn2(II,II) center in each subunit having EPR properties similar to those observed in Mn-catalases. The principal physiologic role of arginase is catalyzing the hydrolytic cleavage of L-arginine to produce L-ornithine and urea. Here we demonstrate that arginase catalyzes the disproportionation of hydrogen peroxide by a redox mechanism analogous to Mn-catalases, but at rates that are 10-5 to 10-6 of k(cat) for the Mn-catalases, and also exhibits peroxidase activity. The dinuclear Mn2(II,II) center is essential for maximal catalase activity, since both the H101N and H126N mutant arginases containing only one Mn(II)/subunit have catalase activities that are <3% of that for the wild- type enzyme. Like the Mn-catalases, the catalase activity of arginase is not inhibited by millimolar concentrations of CN-, the most potent inhibitor of heme catalases, or by EDTA, a chelator of free metal ions. The catalase activity of arginase is not significantly inhibited by C1- or F-, in contrast to Mn-catalases, while potent inhibitors of the hydrolytic activity are also effective inhibitors of the catalase activity. These results suggest that lower affinity of hydrogen peroxide to the active site of arginase contributes to the lower catalase activity. EPR spectroscopy reveals that potent inhibitors of the hydrolytic reaction, including N(ω)-hydroxy-L- arginine, L-lysine, and L-valine, decouple the electronic interaction between the Mn2+ ions, most probably by removing a μ-bridging ligand or by increasing the intermanganese separation. The capacity for arginase to deliver a hydroxide ion to hydrolyze the L-arginine substrate is suggested to arise from a 'dinuclear effect', wherein the two metal ions contribute more or less equivalently in deprotonation of metal-bound water molecule. Structure-reactivity analyses of these reactions will provide insights into the factors that control redox versus hydrolytic function in dimanganese clusters.
AB - Rat liver arginase contains a dinuclear Mn2(II,II) center in each subunit having EPR properties similar to those observed in Mn-catalases. The principal physiologic role of arginase is catalyzing the hydrolytic cleavage of L-arginine to produce L-ornithine and urea. Here we demonstrate that arginase catalyzes the disproportionation of hydrogen peroxide by a redox mechanism analogous to Mn-catalases, but at rates that are 10-5 to 10-6 of k(cat) for the Mn-catalases, and also exhibits peroxidase activity. The dinuclear Mn2(II,II) center is essential for maximal catalase activity, since both the H101N and H126N mutant arginases containing only one Mn(II)/subunit have catalase activities that are <3% of that for the wild- type enzyme. Like the Mn-catalases, the catalase activity of arginase is not inhibited by millimolar concentrations of CN-, the most potent inhibitor of heme catalases, or by EDTA, a chelator of free metal ions. The catalase activity of arginase is not significantly inhibited by C1- or F-, in contrast to Mn-catalases, while potent inhibitors of the hydrolytic activity are also effective inhibitors of the catalase activity. These results suggest that lower affinity of hydrogen peroxide to the active site of arginase contributes to the lower catalase activity. EPR spectroscopy reveals that potent inhibitors of the hydrolytic reaction, including N(ω)-hydroxy-L- arginine, L-lysine, and L-valine, decouple the electronic interaction between the Mn2+ ions, most probably by removing a μ-bridging ligand or by increasing the intermanganese separation. The capacity for arginase to deliver a hydroxide ion to hydrolyze the L-arginine substrate is suggested to arise from a 'dinuclear effect', wherein the two metal ions contribute more or less equivalently in deprotonation of metal-bound water molecule. Structure-reactivity analyses of these reactions will provide insights into the factors that control redox versus hydrolytic function in dimanganese clusters.
KW - Arginase
KW - Catalase
KW - Manganoenzymes
KW - Peroxidase
UR - http://www.scopus.com/inward/record.url?scp=12644291934&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=12644291934&partnerID=8YFLogxK
U2 - 10.1007/s007750050154
DO - 10.1007/s007750050154
M3 - Article
AN - SCOPUS:12644291934
VL - 2
SP - 433
EP - 443
JO - Journal of Biological Inorganic Chemistry
JF - Journal of Biological Inorganic Chemistry
SN - 0949-8257
IS - 4
ER -