Structural insights into the hydrolysis of cellular nitric oxide synthase inhibitors by dimethylarginine dimethylaminohydrolase.
Nitric oxide synthase is inhibited by asymmetric NG-methylated derivatives of arginine whose cellular levels are controlled in part by dimethylarginine dimethylaminohydrolase (DDAH, EC 3.5.3.18). Levels of asymmetric NG,NG-dimethylarginine (ADMA) are known to correlate with certain disease states. Here, the first structure of a DDAH shows an unexpected similarity to arginine:glycine amidinotransferase (EC 2.1.4.1) and arginine deiminase (EC 3.5.3.6), thus defining a superfamily of arginine-modifying enzymes. The identification of a Cys-His-Glu catalytic triad and the structures of a Cys to Ser point mutant bound to both substrate and product suggest a reaction mechanism. Comparison of the ADMA-DDAH and arginine-amidinotransferase complexes reveals a dramatic rotation of the substrate that effectively maintains the orientation of the scissile bond of the substrate with respect to the catalytic residues. The DDAH structure will form a basis for the rational design of selective inhibitors, which are of potential use in modulating NO synthase activity in pathological settings.
Murray-Rust
J
J
School of Crystallography, Birkbeck, Malet Street, London WC1E 7HX, UK.
Leiper
J
J
McAlister
M
M
Phelan
J
J
Tilley
S
S
Santa Maria
J
J
Vallance
P
P
McDonald
N
N
D000581:Amidohydrolases; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D001665:Binding Sites; D002384:Catalysis; D002956:Citrulline / Q000378:metabolism; D018360:Crystallography, X-Ray; D019281:Dimerization; D004791:Enzyme Inhibitors / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D006860:Hydrogen Bonding; D006867:Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006868:Hydrolysis; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D017354:Point Mutation / Q000235:genetics; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D012399:Rotation; D016415:Sequence Alignment; D013379:Substrate Specificity
D004791:Enzyme Inhibitors; D008024:Ligands; D002956:Citrulline; D019001:Nitric Oxide Synthase; D006867:Hydrolases; D000581:Amidohydrolases; C059999:dimethylargininase