Catalase from the white-spotted flower chafer, Protaetia brevitarsis: cDNA sequence, expression, and functional characterization

Catalase, which is one of the key enzymes of the cellular antioxidant defense system, prevents free hydroxyl radical formation by breaking down hydrogen peroxide into oxygen and water. Here, we show the cloning and characterization of a catalase gene in a coleopteran insect. This gene was isolated by searching the white-spotted flower chafer Protaetia brevitarsis cDNA library, and the gene itself encodes a protein of 505 amino acids in length, named PbCat. PbCat shows high similarities to the insect catalase genes known to date. The recombinant PbCat, which is expressed as a 56-kDa polypeptide in baculovirus-infected insect Sf9 cells, shows the highest activity at 30 °C and pH 7.0. Northern and Western blot analyses revealed the presence of PbCat in all tissues examined, showing its ubiquitous expression. P. brevitarsis larvae in which H2O2 was overloaded, showed a marked up-regulation in PbCat expression. Moreover, P. brevitarsis larvae showed an apparent increase in PbCat expression even after a wounding through injection. These results indicate that PbCat is up-regulated after wounding and oxidative pressure induced by H2O2, reflecting an important role of PbCat in H2O2 scavenging.