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Journal of Bacteriology, February 2001, p. 1434-1440, Vol. 183, No. 4
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.4.1434-1440.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Multiple Catalase Genes Are Differentially Regulated in Aspergillus nidulans

Laura Kawasaki and Jesús Aguirre*

Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510 México, D. F., Mexico

Received 4 August 2000/Accepted 21 November 2000

Detoxification of hydrogen peroxide is a fundamental aspect of the cellular antioxidant responses in which catalases play a major role. Two differentially regulated catalase genes, catA and catB, have been studied in Aspergillus nidulans. Here we have characterized a third catalase gene, designated catC, which predicts a 475-amino-acid polypeptide containing a peroxisome-targeting signal. With a molecular mass of 54 kDa, CatC shows high similarity to other small-subunit monofunctional catalases and is most closely related to catalases from other fungi, Archaea, and animals. In contrast, the CatA (~84 kDa) and CatB (~79 kDa) enzymes belong to a family of large-subunit catalases, constituting a unique fungal and bacterial group. The catC gene displayed a relatively constant pattern of expression, not being induced by oxidative or other types of stress. Targeted disruption of catC eliminated a constitutive catalase activity not detected previously in zymogram gels. However, a catalase activity detected in catA catB mutant strains during late stationary phase was still present in catC and catABC null mutants, thus demonstrating the presence of a fourth catalase, here named catalase D (CatD). Neither catC nor catABC triple mutants showed any developmental defect, and both mutants grew as well as wild-type strains in H2O2-generating substrates, such as fatty acids, and/or purines as the sole carbon and nitrogen sources, respectively. CatD activity was induced during late stationary phase by glucose starvation, high temperature, and, to a lesser extent, H2O2 treatment. The existence of at least four differentially regulated catalases indicates a large and regulated capability for H2O2 detoxification in filamentous fungi.

* Corresponding author. Mailing address: Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-242, 04510 México, D. F., Mexico. Phone: (525) 622-5651. Fax: (525) 622-5630. E-mail: jaguirre{at}ifisiol.unam.mx.

Journal of Bacteriology, February 2001, p. 1434-1440, Vol. 183, No. 4
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.4.1434-1440.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


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