Date of Thesis Acceptance
Major Department or Program
PcpA is a bacterial non-heme Fe(II) enzyme that oxidatively cleaves 2,6-dichlorohydroquinone as a part of the pentachlorophenol (PCP) degradation pathway of Sphingobium chlorophenolicum. It has been shown to be specific for ortho-dihalohydroquinones. Possible sources of this specificity include the substrate pKa, and halogen bonding and/or metal-halogen secondary bonding, both of which depend upon halogen polarizability. Substrate binding titrations showed a similar small shift in pKa values between the free substrate and the substrate bound to the enzyme for all substrates. This suggests that PcpA may lack an active site base needed to deprotonate the substrate, in contrast to the closely related catechol extradiol dioxygenase enzymes. Steady-state kinetic studies showed that 2,6-difluorohydroquinone is a poor substrate, similar to 2,6-methylhydroquinone, unlike 2,6-dichloro- and 2,6- dibromohydroquinone. The pH dependence of the kinetics of these substrates provides additional insights into the role of substrate pKa. Together, these studies suggest that both a polarizable halogen substituent and the pKa of the substrate play important roles in defining the substrate specificity of PcpA.
Hydrogen-ion concentration (pH) -- Measurement, Polarization -- Halogens, Ferric oxide (Fe(II)), Halogen compounds, Enzymes -- Analysis, Chemical kinetics -- Data processing, Whitman College 2015 -- Dissertation collection -- Chemistry Department
Whitman Community Accessible Thesis
If you have questions about permitted uses of this content, please contact the ARMINDA administrator
Burrows, Julia Elise, "The role of halogen substituents and substrate pKa in defining the substrate specificity of 2,6-dichlorohydroquinone-1,2-dioxygenase (PcpA)" (2015). Honors Theses. 118.
Available for download on Saturday, May 13, 2017
In Copyright. URI: http://rightsstatements.org/vocab/InC/1.0/
This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).