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Licensed Unlicensed Requires Authentication Published by De Gruyter June 1, 2005

Neurospora crassa Catalases, Singlet Oxygen and Cell Differentiation

  • L. Peraza and W. Hansberg
From the journal Biological Chemistry

Abstract

The morphogenetic transitions of the N. crassa asexual life cycle are responses to a hyperoxidant state in which probably singlet oxygen is generated. Induction of catalase activity and catalase oxidation by singlet oxygen are consequences of this recurrent hyperoxidant state. Here the biochemical properties and regulation of two large monofunctional catalases are reviewed, and a new catalaseperoxidase gene and activity is described. Catalase-3 is associated to growing and Catalase-1 to nongrowing cells. Under stressful conditions one of these catalases is synthesized, depending on whether growth can be continued or a resistant cell has to be made. The catalaseperoxidase Catalase-2 was possibly derived from a bacterial enzyme. In contrast to the other catalases, Catalase-2 had catalase and peroxidase activity. Catalase-2 was expressed under conditions in which vacuolization of hyphae is observed. All three enzymes have a chlorin in its active site instead of ferroprotoheme IX and are resistant to molar concentrations of hydrogen peroxide. These and all other catalases tested so far are oxidized by singlet oxygen, probably at the heme moiety. The catalase activity is virtually unaffected by oxidation, but the enzymes are probably degraded more rapidly than the unmodified ones.

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Published Online: 2005-06-01
Published in Print: 2002-04-12

Copyright © 2002 by Walter de Gruyter GmbH & Co. KG

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