The cysteine dioxygenase homologue from Pseudomonas aeruginosa is a 3-mercaptopropionate dioxygenase.
Thiol dioxygenation is the initial oxidation step that commits a thiol to important catabolic or biosynthetic pathways. The reaction is catalyzed by a family of specific non-heme mononuclear iron proteins each of which is reported to react efficiently with only one substrate. This family of enzymes includes cysteine dioxygenase, cysteamine dioxygenase, mercaptosuccinate dioxygenase, and 3-mercaptopropionate dioxygenase. Using sequence alignment to infer cysteine dioxygenase activity, a cysteine dioxygenase homologue from Pseudomonas aeruginosa (p3MDO) has been identified. Mass spectrometry of P. aeruginosa under standard growth conditions showed that p3MDO is expressed in low levels, suggesting that this metabolic pathway is available to the organism. Purified recombinant p3MDO is able to oxidize both cysteine and 3-mercaptopropionic acid in vitro, with a marked preference for 3-mercaptopropionic acid. We therefore describe this enzyme as a 3-mercaptopropionate dioxygenase. Mössbauer spectroscopy suggests that substrate binding to the ferrous iron is through the thiol but indicates that each substrate could adopt different coordination geometries. Crystallographic comparison with mammalian cysteine dioxygenase shows that the overall active site geometry is conserved but suggests that the different substrate specificity can be related to replacement of an arginine by a glutamine in the active site.
From the Departments of Chemistry and.
Egor P
EP
Tchesnokov
From the Departments of Chemistry and.
Matthias
M
Fellner
From the Departments of Chemistry and.
Eleni
E
Siakkou
Biochemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand.
Torsten
T
Kleffmann
Biochemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand.
Lois W
LW
Martin
From the Departments of Chemistry and.
Sekotilani
S
Aloi
Biochemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand.
Iain L
IL
Lamont
Biochemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand.
Sigurd M
SM
Wilbanks
From the Departments of Chemistry and guy.jameson@otago.ac.nz.
Guy N L
GN
Jameson
D015097:3-Mercaptopropionic Acid / Q000737:chemistry*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D001665:Binding Sites; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000737:chemistry; D050558:Cysteine Dioxygenase / Q000737:chemistry*; D007501:Iron / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010100:Oxygen / Q000737:chemistry; D010101:Oxygen Consumption; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011550:Pseudomonas aeruginosa / Q000201:enzymology*; D017386:Sequence Homology, Amino Acid; D013053:Spectrophotometry; D013379:Substrate Specificity; D013438:Sulfhydryl Compounds
D001426:Bacterial Proteins; D010455:Peptides; D013438:Sulfhydryl Compounds; D015097:3-Mercaptopropionic Acid; D007501:Iron; D050558:Cysteine Dioxygenase; D003545:Cysteine; D010100:Oxygen
Mossbauer spectroscopy; Pseudomonas aeruginosa (P. aeruginosa); crystal structure; dioxygenase; enzyme kinetics; substrate specificity