In vivo role of catalase-peroxidase in Synechocystis sp. strain PCC 6803

Martin Tichy, Willem Vermaas

Research output: Contribution to journalArticle

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Abstract

The katG gene coding for the only catalase-peroxidase in the cyanobacterium Synechocystis sp. strain PCC 6803 was deleted in this organism. Although the rate of H2O2 decomposition was about 30 times lower in the ΔkatG mutant than in the wild type, the strain had a normal phenotype and its doubling time as well as its resistance to H2O2 and methyl viologen were indistinguishable from those of the wild type. The residual H2O2 scavenging capacity was more than sufficient to deal with the rate of H2O2 production by the cell, estimated to be less than 1% of the maximum rate of photosynthetic electron transport in vivo. We propose that catalase- peroxidase has a protective role against environmental H2O2 generated by algae or bacteria in the ecosystem (for example, in mats). This protective role is most apparent at a high cell density of the cyanobacterium. The residual H2O2-scavenging activity in the ΔkatG mutant was a light- dependent peroxidase activity. However, neither glutathione peroxidase nor ascorbate peroxidase accounted for a significant part of this H2O2- scavenging activity. When a small thiol such as dithiothreitol was added to the medium, the rate of H2O2 decomposition in the ΔkatG mutant increased more than 10-fold, indicating that a thiol-specific peroxidase, for which thioredoxin may be the physiological electron donor, is present. Oxidized thioredoxin is likely to be reduced again by photosynthetic electron transport. Therefore, under laboratory conditions, there are only two enzymatic mechanisms for H2O2 decomposition present in Synechocystis sp. strain PCC 6803. One is catalyzed by a catalase-peroxidase, and the other is catalyzed by thiol-specific peroxidase.

Original languageEnglish (US)
Pages (from-to)1875-1882
Number of pages8
JournalJournal of Bacteriology
Volume181
Issue number6
StatePublished - Mar 1999

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Synechocystis
Catalase
Peroxidase
Sulfhydryl Compounds
Cyanobacteria
Electron Transport
Ascorbate Peroxidases
Peroxiredoxins
Thioredoxins
Paraquat
Dithiothreitol
Glutathione Peroxidase
Ecosystem
Cell Count
Electrons
Bacteria
Phenotype
Light
Genes

ASJC Scopus subject areas

  • Applied Microbiology and Biotechnology
  • Immunology

Cite this

In vivo role of catalase-peroxidase in Synechocystis sp. strain PCC 6803. / Tichy, Martin; Vermaas, Willem.

In: Journal of Bacteriology, Vol. 181, No. 6, 03.1999, p. 1875-1882.

Research output: Contribution to journalArticle

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