Skip to main content
Home Whitman College Penrose Library | Arminda Collections

Main menu

  • Home
  • Browse Collections
  • About
  • Login
  1. Home
  2. Honors Theses
  3. The role of halogen substituents and substrate pKa̳ in defining the substrate specificity of 2,6-dichlorohydroquinone-1,2-dioxygenase (PcpA)
Title

The role of halogen substituents and substrate pKa̳ in defining the substrate specificity of 2,6-dichlorohydroquinone-1,2-dioxygenase (PcpA)

    Item Description
    Limited Access
    The author(s) chose to restrict access to this thesis to current Whitman students, faculty, and staff. Please log in to view it.
    Linked Agent
    Creator (cre): Burrows, Julia Elise
    Advisor (adv): Machonkin, Tim
    Department (dpt): Whitman College. Chemistry Department
    Date
    May 13, 2015
    Graduation Year
    2015
    Abstract

    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 pKa̳, 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 pKa̳ 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 pKa̳. Together, these studies suggest that both a polarizable halogen substituent and the pKa̳ of the substrate play important roles in defining the substrate specificity of PcpA.

    Subject
    Hydrogen-ion concentration -- Measurement -- pH
    Polarization (Light) -- Halogens
    Ferric oxide -- Fe(II)
    Halogen compounds
    Enzymes -- Analysis
    Chemical kinetics -- Data processing
    Science
    Academic theses
    Whitman College 2015 -- Dissertation collection -- Chemistry Department
    Genre
    Theses
    Extent
    68 pages
    Permanent URL
    http://works.whitman.edu/20151120
    Rights
    http://rightsstatements.org/vocab/InC/1.0/
    Contact Us

    If you have questions about permitted uses of this content, please contact the Arminda administrator: http://works.whitman.edu/contact-arminda

    8027612
    Home Whitman College Penrose Library | Arminda Collections

    Footer menu

    • About
    • Author FAQ
    • Contact Us
    • List of Collections
    • Policies
    • Terms of Use