Analysis of the genome of the human pathogen, Aspergillus,fumigatus, revealed the presence of several putative glutathione transferase (GST) open reading frames. Three A. fumigatus GST genes, termed gstA, B, and C, were cloned and recombinant proteins expressed in Escherichia coli. Functional analysis of recombinant gstA-C confirms that the enzymes exhibit GST activity and glutathione peroxidase activity. RT-PCR confirmed low basal expression of gstA and gstC which was markedly up-regulated (at least 4x-10x) in the presence of either H2O2 or 1-chloro-2,4-dinitrobenzene (CDNB). GstB expression was only observed in the presence of CDNB. These results demonstrate for the first time the existence of three functional GSTs in A. fumigatus and strongly suggest a role for these enzymes in the response of the organism to both oxidative stress and xenobiotic presence. (c) 2005 Elsevier Inc. All rights reserved.