Nucleotide Inhibition of Glyoxalase II Metadata

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Title

  • Main Title Nucleotide Inhibition of Glyoxalase II

Creator

  • Author: Gillis, Glen S
    Creator Type: Personal

Contributor

  • Chair: Norton, Scott J.
    Contributor Type: Personal
    Contributor Info: Major Professor
  • Committee Member: Massarachia, Ruth Anne
    Contributor Type: Personal
  • Committee Member: Donahue, Manus J.
    Contributor Type: Personal
  • Committee Member: Chapman, Kent D.
    Contributor Type: Personal

Publisher

  • Name: University of North Texas
    Place of Publication: Denton, Texas

Date

  • Creation: 1999-05

Language

  • English

Description

  • Content Description: The glyoxalase system mediates the conversion of methylglyoxal, a toxic ketoaldehyde, to D-lactic acid. The system is composed of two enzymes, glyoxalase I (Glo-I) and glyoxalase II (Glo-II), and exhibits an absolute requirement for a catalytic quantity of glutathione (GSH). Glo-I catalyzes the isomerization of a hemithioacetal, formed non-enzymatically from methylglyoxal and GSH, to the corresponding a -D-hydroxyacid thioester, s-D-lactoylglutathione (SLG). Glo-II catalyzes the irreversible breakdown of SLG to D-lactate and GSH. We have observed that ATP or GTP significantly inhibits the Glo-II activity of tissue homogenates from various sources. We have developed a rapid, one step chromatography procedure to purify Glo-II such that the purified enzyme remains "sensitive" to inhibition by ATP or GTP (Glo-II-s). Studies indicate that inhibition of Glo-II-s by nucleotides is restricted to ATP, GTP, ADP, and GDP, with ATP appearing most effective. Kinetics studies have shown that ATP acts as a partial non-competitive inhibitor of Glo-II-s activity, and further suggest that two kinetically distinguishable forms of the enzyme exist. The sensitivity of pure Glo-II-s to nucleotide inhibition is slowly lost on storage even at -80° C. This loss is accelerated at higher temperatures or in the presence of ATP. Kinetics studies on the resultant "insensitive" enzyme (Glo-II-i) show that a significant reduction of the affinity of the enzyme for the substrate, SLG, occurs and further suggest that only one form of the enzyme is kinetically distinguishable after "de-sensitization". Tryptophan fluorescence studies of the two enzyme preparations suggest that a subtle conformational change in the enzyme has occurred during de-sensitization. We have also observed that Glo-II-i is "resensitized" to nucleotide inhibition after incubation in the presence of a reagent that reduces disulfide bonds. The resensitized enzyme exhibits an increased KM value similar to that of the original Glo-II-s. Kinetics studies show that ATP or GTP again act as partial non-competitive inhibitors of the resensitized enzyme and suggest that only one form of the enzyme is present. The physiological significance of the two enzyme forms is discussed.

Subject

  • Library of Congress Subject Headings: Glyoxalase.
  • Library of Congress Subject Headings: Nucleotides.
  • Library of Congress Subject Headings: Glutathione.
  • Keyword: glyoxalase I
  • Keyword: glutathione
  • Keyword: ATP
  • Keyword: GTP
  • Keyword: glyoxalase II

Collection

  • Name: UNT Theses and Dissertations
    Code: UNTETD

Institution

  • Name: UNT Libraries
    Code: UNT

Rights

  • Rights Access: public
  • Rights License: copyright
  • Rights Holder: Gillis, Glen S
  • Rights Statement: Copyright is held by the author, unless otherwise noted. All rights reserved.

Resource Type

  • Thesis or Dissertation

Format

  • Text

Identifier

  • OCLC: 45003473
  • UNT Catalog No.: b2226120
  • Archival Resource Key: ark:/67531/metadc2183

Degree

  • Degree Name: Doctor of Philosophy
  • Degree Level: Doctoral
  • Degree Discipline: Biochemistry
  • Academic Department: Department of Biological Sciences
  • Degree Grantor: University of North Texas

Note