A eukaryote without catalase-containing microbodies: Neurospora crassa exhibits a unique cellular distribution of its four catalases.
Microbodies usually house catalase to decompose hydrogen peroxide generated within the organelle by the action of various oxidases. Here we have analyzed whether peroxisomes (i.e., catalase-containing microbodies) exist in Neurospora crassa. Three distinct catalase isoforms were identified by native catalase activity gels under various peroxisome-inducing conditions. Subcellular fractionation by density gradient centrifugation revealed that most of the spectrophotometrically measured activity was present in the light upper fractions, with an additional small peak coinciding with the peak fractions of HEX-1, the marker protein for Woronin bodies, a compartment related to the microbody family. However, neither in-gel assays nor monospecific antibodies generated against the three purified catalases detected the enzymes in any dense organellar fraction. Furthermore, staining of an N. crassa wild-type strain with 3,3'-diaminobenzidine and H(2)O(2) did not lead to catalase-dependent reaction products within microbodies. Nonetheless, N. crassa does possess a gene (cat-4) whose product is most similar to the peroxisomal type of monofunctional catalases. This novel protein indeed exhibited catalase activity, but was not localized to microbodies either. We conclude that N. crassa lacks catalase-containing peroxisomes, a characteristic that is probably restricted to a few filamentous fungi that produce little hydrogen peroxide within microbodies.
Schliebs
Wolfgang
W
Institut für Physiologische Chemie, Abt. Systembiochemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
Würtz
Christian
C
Kunau
Wolf-Hubert
WH
Veenhuis
Marten
M
Rottensteiner
Hanspeter
H
D000595:Amino Acid Sequence; D002374:Catalase / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology; D005658:Fungi / Q000201:enzymology; D020676:Glyoxysomes / Q000201:enzymology; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D015151:Immunoblotting; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D008830:Microbodies / Q000201:enzymology*; D008856:Microscopy, Fluorescence; D016253:Microscopy, Immunoelectron; D008928:Mitochondria / Q000201:enzymology; D008969:Molecular Sequence Data; D009492:Neurospora crassa / Q000201:enzymology* / Q000235:genetics / Q000648:ultrastructure; D021382:Protein Sorting Signals / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D007527:Isoenzymes; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D006861:Hydrogen Peroxide; D002374:Catalase