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The membrane-bound formaldehyde dehydrogenase from Methylococcus capsulatus Bath is a homotetramer consisting of 49,500 dalton each subunits. The enzyme oxidizes formaldehyde to formate and uses pyrroloquinoline quinone as its redox cofactor.

Research was conducted to examine the structural gene and polypeptide for high-molecular-mass multi-c-heme cytochromes from Methylococcus capsulatus Bath. Electron paramagnetic resonance spectrum and degenerate oligonucleotide probe were used to prove the presence of multiple low spin and to identify a DNA fragment from M. capsulatus, respectively. Results indicate that cytochrome C5530 and the gene products of ORF3 and ORF1 belong to a novel class of c-type cytochrome.

P460 cytochromes catalyze the oxidation of hydroxylamine to nitrite. A degenerate oligonucleotide probe was synthesized using the N-terminal amino acid sequence of cytochrome P460 and applied in the identification of a DNA fragment from M. capsulatus Bath that contains cyp, the gene encoding cytochrome P460. The overall sequence similarity of the P460 cytochromes from M. capsulatus Bath and N. europaea was low, even though short regions conserved residues are found in both proteins. Both terminals have a C-terminal, c-heme binding motif and a conserved lysine residue.

The gene cycA encoding the tetraheme cytochrome c554 of Nitrosomonas europaea is present in three copies per genome and the cytochrome c554 represents a new class of tetraheme c cytochromes. Southern blot sequence probes reveal that the gene cluster consists of hao, cycA and ORF2 genes and organization of these genes for three proteins results in ammonia oxidation in N. europaea.

The sequence of the entire hao gene cluster that exists as a single copy in the genome of Nitrosococcus oceani and compare it to the hao gene clusters of Nitrosospira multiforms and Nitrosomonas europaea is presented. The analyses of gene cluster organization and phylogenetic analyses of the protein sequences encoded by genes in the hao gene cluster are described.

The properties of a site-specific mutant form of PchF were studied to examine the roles of Arg474 in p-cresol methylhydroxylase (PCMH). The result indicates that these mutant proteins retain all of the basic properties of the corresponding wild-type forms of PchF.