Anti-GSTZ1 monoclonal antibody, clone 2H23

Objectives The zeta-class glutathione transferase GSTZ1-1 catalyses the glutathione-dependent isomerization of maleylacetoacetate to fumarylacetoacetate in the tyrosine catabolic pathway and the biotransformation of alpha-halo acids, including dichloroacetic acid (DCA). Genetic polymorphisms in the coding sequence of GSTZ1 result in significant changes in enzyme function, and deficiency of GSTZ1-1 in mice causes induction of a range of Phase-II enzymes. In this study, the potential for polymorphisms in regulatory sequences to alter gene transcription was investigated. Methods A total of 10 single-nucleotide polymorphisms (SNP) were identified in African and Australian European subjects in a region extending 1.5-kb upstream of the GSTZ1 start of transcription. These SNPs formed at least 10 haplotypes and only two were shared between the two population samples. The effect of these SNPs on gene expression was evaluated by the transient expression of specific alleles fused to a luciferase reporter gene. Results Of the 10 SNPs identified, only -1002 G > A and -289 C > T caused significant changes in promoter activity. The -1002 G > A SNP converts a v-Myb site to a S8 homeodomain (Prx2) site, and the -289 C > T SNP abolishes an Egr1 binding site. Conclusion These SNPs may alter GSTZ1 expression, which may alter the pharmacokinetics of DCA, which is used therapeutically for the treatment of lactic acidosis. Pharmacogenetics and Genomics 16: 307-313 (c) 2006 Lippincott Williams & Wilkins.

Zeta-class glutathione transferases (GSTZs) were recently discovered by a bioinformatics approach and the availability of human expressed sequence tag databases. Although GSTZ showed little activity with conventional GST substrates (1-chloro-2,4-dinitrobenzene; organic hydroperoxides), GSTZ was found to catalyze the oxygenation of dichloroacetic acid (DCA) to glyoxylic acid and the cis-trans isomerization of maleylacetoacetate to fumarylacetoacetate. Hence, GSTZ plays a critical role in the tyrosine degradation pathway and in alpha-haloacid metabolism. The GSTZ-catalyzed biotransformation of DCA is of particular interest, because DCA is used in the human clinical management of congenital lactic acidosis and because DCA is a common drinking water contaminant. Substrate selectivity studies showed that GSTZ catalyzes the glutathione-dependent biotransformation of a range of dihaloacetic acids along with fluoroacetic acid, 2-halopropanoic acids, and 2,2-dichloropropanoic acid. Human clinical studies showed that the elimination half-life of DCA increases with repeated doses of DCA; also, rats given DCA show low GSTZ activity with DCA as the substrate. DCA was found to be a mechanism-based inactivator of GSTZ, and proteomic studies showed that Cys-16 of human GSTZ1-1 is covalently modified by a reactive intermediate that contains glutathione and the carbon skeleton of DCA. Bioinformatics studies also showed the presence of at least four polymorphic variants of human GSTZ; these variants differ considerably in the rates of catalysis and in their susceptibility to inactivation by DCA. Finally, Gstz1(-/-) mouse strains have been developed; these mice fail to biotransform DCA or maleylacetone. Although the mice have no obvious phenotype, a high incidence of lethality is observed in young mice given phenylalanine in their drinking water. Gstz1(-/-) mice should prove useful in expanding the role of GSTZ in alpha-haloacid metabolism and in the tyrosine degradation pathway.