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The human glutathione transferase P1-1 specific inhibitor TER 117 designed for overcoming cytostatic-drug resistance is also a strong inhibitor of glyoxalase I
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry.
2000 (English)In: Molecular Pharmacology, ISSN 0026-895X, E-ISSN 1521-0111, Vol. 57, no 3, 619-624 p.Article in journal (Refereed) Published
Abstract [en]

gamma-L-Glutamyl-S-(benzyl)-L-cysteinyl-R-(-)-phenylglycine (TER 117) has previously been developed for selective inhibition of human glutathione S-transferase P1-1 (GST P1-1) based on the postulated contribution of this isoenzyme to the development of drug resistance in cancer cells. In the present investigation, the inhibitory effect of TER 117 on the human glyoxalase system was studied. Although designed as an inhibitor specific for GST P1-1, TER 117 also competitively inhibits glyoxalase I (K(I) = 0.56 microM). In contrast, no inhibition of glyoxalase II was detected. Reduced glyoxalase activity is expected to raise intracellular levels of toxic 2-oxoaldehydes otherwise eliminated by glyoxalase I. The resulting toxicity would accompany the potentiation of cytostatic drugs, caused by inhibition of the detoxication effected by GST P1-1. TER 117 was designed for efficient inhibition of the most abundant form GST P1-1/Ile105. Therefore, the inhibitory effect of TER 117 on a second allelic variant GST P1-1/Val105 was also studied. TER 117 was shown to competitively inhibit both GST P1-1 variants. The apparent K(I) values at glutathione concentrations relevant to the intracellular milieu were in the micromolar range for both enzyme forms. Extrapolation to free enzyme produced K(I) values of approximately 0.1 microM for both isoenzymes, reflecting the high affinity of GST P1-1 for the inhibitor. Thus, the allelic variation in position 105 of GST P1-1 does not affect the inhibitory potency of TER 117. The inhibitory effects of TER 117 on GST P1-1 and glyoxalase I activities may act in synergy in the cell and improve the effectiveness of chemotherapy.

Place, publisher, year, edition, pages
2000. Vol. 57, no 3, 619-624 p.
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:uu:diva-89716PubMedID: 10692504OAI: oai:DiVA.org:uu-89716DiVA: diva2:161424
Available from: 2002-03-27 Created: 2002-03-27 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Exploring the Functional Plasticity of Human Glutathione Transferases: Allelic Variants, Novel Isoenzyme and Enzyme Redesign
Open this publication in new window or tab >>Exploring the Functional Plasticity of Human Glutathione Transferases: Allelic Variants, Novel Isoenzyme and Enzyme Redesign
2002 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Glutathione transferases (GSTs) make up a superfamily that is involved in the cellular defense against various reactive compounds by catalyzing the conjugation of glutathione to electrophilic centra. Members of this family have also been implicated in different facets of biological signaling.

The gene encoding human GST P1-1 is polymorphic, resulting in variant amino acid residues in positions 105 and 114. The role of the polymorphism in the active-site residue 105 on enzyme stability and activity with various substrates was investigated. A valine instead of an isoleucine in position 105 decreased the thermal stability of the enzyme. The effect on enzyme activity was dependent on the substrate and reaction studied. With some substrates tested, such as carcinogenic diolepoxides derived from polyaromatic hydrocarbons, GST P1-1/Val105 displayed the highest catalytic efficiency. In contrast, with 1-chloro-2,4-dinitrobenzene, the GST P1-1/Ile105 showed higher activity. Residue 105 was mutated to alanine and tryptophan to investigate the role of size and hydrophobicity of residue 105 on enzyme properties. Generally, a smaller amino acid in position 105 gave increased activity with large substrates. Clearly, residue 105 of GST P1-1 helps to determine the substrate selectivity of the enzyme. In addition, more voluminous amino acids in position 105 increase the thermal stability of the enzyme.

GST P1-1 is believed to contribute to the development of drug resistance in cancer cells. The affinity of GST P1-1 for TER 117, designed to inhibit GST P1-1 in tumors, was not affected by the variability in position 105. TER 117 was found to be a potent inhibitor of glyoxalase I as well.

The cDNA encoding GST A3-3 was isolated from a placental cDNA library. GST A3-3 was heterologously expressed, purified and found to catalyze efficiently the double-bond isomerization of Δ5-androstene-3,17-dione and Δ5-pregnene-3,20-dione, reactions taking place in the biosynthesis of the steroid hormones testosterone and progesterone, respectively. GST A3-3 was found to be selectively expressed in steroidogenic tissues, suggesting that this enzyme is involved in the production of steroid hormones. The presence of both the hydroxyl group of the active-site tyrosine 9 and the thiolate form of glutathione, acting as a cofactor, is important for high double-bond isomerase activity. A leucine in position 111 appears to have a major role in productive binding of the steroid substrate but also residues F10 and A216 are determinants for the high isomerase activity.

GST A2-2 is a poor catalyst of the steroid double-bond isomerization of Δ5-androstene-3,17-dione as compared to GST A3-3, despite 88% sequence identity. GST A2-2 was redesigned to a highly efficient double-bond isomerase by mutating five active-site residues to the corresponding residues of GST A3-3. This demonstrates the functional plasticity of GSTs and the power of a rational approach to redesign of these enzymes.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2002. 56 p.
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 695
Keyword
Biochemistry, Biokemi
National Category
Biochemistry and Molecular Biology
Research subject
Biochemistry
Identifiers
urn:nbn:se:uu:diva-1858 (URN)91-554-5270-1 (ISBN)
Public defence
2002-04-19, B42, Biomedical Center, Uppsala, 10:15
Opponent
Available from: 2002-03-27 Created: 2002-03-27Bibliographically approved

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