Isolation and expression of the catA gene encoding the major vegetative catalase in Streptomyces coelicolor

We isolated the catA gene for the major vegetative catalase from Streptomyces coelicolor Müller. It encodes a polypeptide of 488 residues (55,440 Da) that is highly homologous to typical monofunctional catalases. We investigated catA expression by analyzing both catA mRNA and catalase activity. catA expression was increased by H2O2 treatment but did not increase during stationary phase. A putative catalase (CatB) cross-reactive with anti-CatA antibody appeared during stationary phase and in the aerial mycelium. Catalase is an oxidoreductase which transfers two electrons to H2O2, decomposing it into O2 and H2O. Most of the cata-lases characterized so far can be classified into one of two types based on their enzymological properties (reference 15 and references therein): monofunctional (typical) catalases and bi-functional catalase-peroxidases. Multiple catalases have been found in organisms such as Escherichia coli (5, 6), Bacillus subtilis (16), Streptomyces coelicolor (13, 14), Saccharomyces cerevisiae (19, 20), and Aspergillus nidulans (17). The role of each enzyme in different stages of the growth of these organ