CHARACTERIZATION OF THE MEMBRANOUS DENITRIFICATION ENZYMES NITRITE REDUCTASE (CYTOCHROME CD(1)) AND COPPER-CONTAINING NITROUS-OXIDE REDUCTASE FROM THIOBACILLUS DENITRIFICANS

Cytochrome cd(1)-nitrite reductase and nitrous oxide reductase of Thio bacillus denitrificans were purified and characterized by biochemical and immunochemical methods. In contrast to the generally soluble natur e of the denitrification enzymes, these two enzymes were isolated from the membrane fraction of T. denitrificans and remained active after s olubilization with Triton X-100. The properties of the membrane-derive d enzymes were similar to those of their soluble counterparts from the same organism. Nitrous oxide reductase activity was inhibited by acet ylene. Nitrite reductase and nitrous oxide reductase cross-reacted wit h antisera raised against the soluble enzymes from Pseudomonas stutzer i. The nirS, norBC, and nosZ genes encoding the cytochrome cd(1)-nitri te reductase, nitric oxide reductase, and nitrous oxide reductase, res pectively, from P. stutzeri hybridized with genomic DNA from T. denitr ificans. Cross-reactivity and similar N-terminal amino acid and gene s equences suggest that the primary structures of the Thiobacillus enzym es are homologous to the soluble proteins from P. stutzeri.