Understanding the Origin of Suicide Inactivation in the Extradiol Dioxygenases Timothy E. Machonkin, Department of Chemistry, Whitman College, Walla Walla, WA 99362
We have re-focussed our efforts to study poorly characterized non-catechol ring-cleaving dioxygenases, especially the hydroquinone dioxygenases that actually FHABAH chlorinated (and even brominated) substrates, PcpA and LinE. We are using a two-pronged approach of studying both the actual enzymes and synthesis of novel model complexes: 1. Biochemical studies of unusual Fe(II)-containing ring-cleaving dioxygenases that cleave chlorinated substrates. Structural model of 2,6-dichlorohydroquinone dioxygenase (PcpA). The overall tertiary structure is shown to the right, the active site to the left
Ring-cleavage of 2,6-dibromohydroquinone by PcpA: 2.5
PCR amplification of the gene of another hydroquinone dioxygenase:
Absorbance
2
H159
H11 E276
1.5
1
H227 Y266
0.5
0 225
250
275
300
325
350
375
400
Wavelength (nm)
2. Fe(II)-containing model complexes that can coordinate phenols that mimic enzyme substrates. Design of ligands to mimic the facial capping triad of ring-cleaving dioxygenases:
R
R Fe
N
N
N R
A
R'
Fe
R N
N
R'
R'
N
N N
N B H
R
B
= vacant site f or substrate, O 2 mimic coordination
R
Paramagnetic NMR spectra of (TACH-o-tol) Fe(II) complexes upon addition of substituted phenols:
Crystal structure of [(TACH-o-tol)FeII(2,6-dichlorophenolate)]OTf:
