Cadmium(II) complexes of the glycerophosphodiester-degrading enzyme GpdQ and a biomimetic N,O ligand.
The glycerophosphodiester-degrading enzyme GpdQ from Enterobacter aerogenes is a promising bioremediator owing to its ability to degrade some organophosphate pesticides and diester products originating from the hydrolysis of nerve agents such as VX. Here, the cadmium derivative of GpdQ was prepared by reconstituting the apoenzyme. Catalytic measurements with (Cd(2+))(2)-GpdQ and the phosphodiester substrate bis(4-nitrophenyl)phosphate yield k(cat) = 15 s(-1). The pK(a) of 9.4, determined from the pH dependence of the catalytic activity, implicates a hydroxide ligand as the catalytic nucleophile. Also prepared was the cadmium-containing biomimetic [Cd(2)((HP)(2)B)(OAc)(2)(OH(2))](PF(6)) (where (HP)(2)B is [2,6-bis([(2-pyridylmethyl)(2-hydroxyethyl)amino]methyl)-4-methylphenol]), which mimics the asymmetry of the metal ion coordination in the active site of GpdQ. The phosphoesterase-like activity of [Cd(2)((HP)(2)B)(OAc)(2)(OH(2))](PF(6)) was studied using the substrate bis(2,4-dinitrophenyl)phosphate, yielding a kinetically relevant pK(a) of 8.9, with k(cat) = 0.004 s(-1). In summary, the model is both an adequate structural and a reasonable functional mimic of GpdQ.
School of Molecular and Microbial Sciences, The University of Queensland, St. Lucia, QLD, 4072, Australia.
Ruth E
RE
Mirams
Sarah J
SJ
Smith
Kieran S
KS
Hadler
David L
DL
Ollis
Gerhard
G
Schenk
Lawrence R
LR
Gahan
D055162:Biocatalysis; D040761:Biomimetic Materials / Q000737:chemistry* / Q000378:metabolism*; D002104:Cadmium / Q000737:chemistry*; D018360:Crystallography, X-Ray; D021902:Enterobacter aerogenes / Q000201:enzymology; D008024:Ligands; D009942:Organometallic Compounds / Q000737:chemistry* / Q000378:metabolism*; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D011199:Potentiometry; D011725:Pyridines / Q000737:chemistry
D008024:Ligands; D009942:Organometallic Compounds; D011725:Pyridines; D002104:Cadmium; D010727:Phosphoric Diester Hydrolases; C038133:glycerophosphodiester phosphodiesterase