Scherer Mario, Wei Huijun, Liese Ralf, Fischer Reinhard
Laboratorium für Mikrobiologie, Philipps-Universität Marburg and Max-Planck-Institut für Terrestrische Mikrobiologie, D-35043 Marburg, Germany.
Eukaryot Cell. 2002 Oct;1(5):725-35. doi: 10.1128/EC.1.5.725-735.2002.
Catalases, peroxidases, and catalase-peroxidases are important enzymes to cope with reactive oxygen species in pro- and eukaryotic cells. In the filamentous fungus Aspergillus nidulans three monofunctional catalases have been described, and a fourth catalase activity was observed in native polyacrylamide gels. The latter activity is probably due to the bifunctional enzyme catalase-peroxidase, which we characterized here. The gene, named cpeA, encodes an 81-kDa polypeptide with a conserved motif for heme coordination. The enzyme comprises of two similar domains, suggesting gene duplication and fusion during evolution. The first 439 amino acids share 22% identical residues with the C terminus. Homologous proteins are found in several prokaryotes, such as Escherichia coli and Mycobacterium tuberculosis (both with 61% identity). In fungi the enzyme has been noted in Penicillium simplicissimum, Septoria tritici, and Neurospora crassa (69% identical amino acids) but is absent from Saccharomyces cerevisiae. Expression analysis in A. nidulans revealed that the gene is transcriptionally induced upon carbon starvation and during sexual development, but starvation is not sufficient to reach high levels of the transcript during development. Besides transcriptional activation, we present evidence for posttranscriptional regulation. A green fluorescent protein fusion protein localized to the cytoplasm of Hülle cells. The Hülle cell-specific expression was dependent on the developmental regulator StuA, suggesting an activating function of this helix-loop-helix transcription factor.
过氧化氢酶、过氧化物酶和过氧化氢酶-过氧化物酶是原核细胞和真核细胞中应对活性氧的重要酶。在丝状真菌构巢曲霉中，已描述了三种单功能过氧化氢酶，并且在天然聚丙烯酰胺凝胶中观察到了第四种过氧化氢酶活性。后者的活性可能归因于双功能酶过氧化氢酶-过氧化物酶，我们在此对其进行了表征。该基因名为cpeA，编码一个81 kDa的多肽，具有保守的血红素配位基序。该酶由两个相似的结构域组成，表明在进化过程中发生了基因复制和融合。前439个氨基酸与C末端有22%的相同残基。在几种原核生物中发现了同源蛋白，如大肠杆菌和结核分枝杆菌（两者的同源性均为61%）。在真菌中，该酶已在简单青霉、小麦壳针孢和粗糙脉孢菌中被发现（氨基酸同源性为69%），但酿酒酵母中不存在。在构巢曲霉中的表达分析表明，该基因在碳饥饿和有性发育过程中受到转录诱导，但饥饿不足以在发育过程中达到高水平的转录本。除了转录激活外，我们还提供了转录后调控的证据。绿色荧光蛋白融合蛋白定位于Hülle细胞的细胞质中。Hülle细胞特异性表达依赖于发育调节因子StuA，表明这种螺旋-环-螺旋转录因子具有激活功能。
