Structural, kinetic, and theoretical studies on models of the zinc-containing phosphodiesterase active center: medium-dependent reaction mechanisms.
Dinuclear zinc(II) complexes [Zn(2)(bpmp)(mu-OH)](ClO(4))(2) (1) and [Zn(2)(bpmp)(H(2)O)(2)](ClO(4))(3) (2) (H-BPMP=2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-methylphenol) have been synthesized, structurally characterized, and pH-driven changes in metal coordination observed. The transesterification reaction of 2-hydroxypropyl p-nitrophenyl phosphate (HPNP) in the presence of the two complexes was studied both in a water/DMSO (70:30) mixture and in DMSO. Complex 2 was not reactive whereas for 1 considerable rate enhancement of the spontaneous hydrolysis reaction was observed. A detailed mechanistic investigation by kinetic studies, spectroscopic measurements ((1)H, (31)P NMR spectroscopy), and ESI-MS analysis in conjunction with ab initio calculations was performed on 1. Based on these results, two medium-dependent mechanisms are presented and an unusual bridging phosphate intermediate is proposed for the process in DMSO.
Selmeczi
Katalin
K
Département de Chimie Moléculaire, Université J. Fourier, Grenoble I, UMR-5250, ICMG FR-2607, CNRS BP-53, 38041 Grenoble, France.
Michel
Carine
C
Milet
Anne
A
Gautier-Luneau
Isabelle
I
Philouze
Christian
C
Pierre
Jean-Louis
JL
Schnieders
David
D
Rompel
Annette
A
Belle
Catherine
C
D001665:Binding Sites; D018360:Crystallography, X-Ray; D004789:Enzyme Activation; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods / Q000592:standards; D008954:Models, Biological; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry; D010727:Phosphoric Diester Hydrolases / Q000737:chemistry*; D012015:Reference Standards; D012260:Ribonucleases / Q000737:chemistry*; D012680:Sensitivity and Specificity; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013237:Stereoisomerism; D015032:Zinc / Q000737:chemistry*
D009942:Organometallic Compounds; D012260:Ribonucleases; D010727:Phosphoric Diester Hydrolases; D015032:Zinc