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J. Bacteriol., Jun 1996, 3578-3584, Vol 178, No. 12
S Mongkolsuk, S Loprasert, P Vattanaviboon, C Chanvanichayachai, S Chamnongpol and N Supsamran
Catalase is an important protective enzyme against H2O2 toxicity. Here, we
report the characterization of a Xanthomonas oryzae pv. oryzae catalase
gene (katX). The gene was localized and its nucleotide sequence was
determined. The gene codes for a 77-kDa polypeptide. The deduced katX amino
acid sequence shares regions of high identity with other monofunctional
catalases in a range of organisms from bacteria to eukaryotes. The
transcriptional regulation of katX was atypical of bacterial monofunctional
kat genes. Northern (RNA) analysis showed that katX transcription was
highly induced by treatments with low concentrations of menadione, a
superoxide generator, and methyl methanesulfonate, a mutagen. It was only
weakly induced by H2O2. Unlike in other bacteria, a high level of catalase
in Xanthomonas spp. provided protection from the growth-inhibitory and
killing effects of H2O2 but not from those of organic peroxides and
superoxide generators. Unexpectedly, heterologous expression of katX in
Escherichia coli was both growth phase and temperature dependent. Catalase
activity in E. coli kat mutants harboring katX on an expression vector was
detectable only when the cells entered the stationary phase of growth and
at 28 degrees C. The patterns of transcription regulation, heterologous
expression, and physiological function of katX are different from
previously studied bacterial kat genes.
Copyright © 1996, American Society for Microbiology
Heterologous growth phase- and temperature-dependent expression and H2O2 toxicity protection of a superoxide-inducible monofunctional catalase gene from Xanthomonas oryzae pv. oryzae
Laboratory of Biotechnology, Chulabhorn Research Institute, Lak Si, Bangkok, Thailand.
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