A new microperoxidase from Marinobacter hydrocarbonoclasticus

The preparation and characterization of a new microperoxidase obtained from proteinase K-treated cytochrome c₅₅₂ from Marinobacter hydrocarbonoclasticus (previously known as Pseudomonas nautica) are presented. This microperoxidase (MMP-5) has novel structural properties relative to previously reported microperoxidases, as the two intervening amino acid (X) residues within the consensual CXXCH c-type heme binding motif are missing, yielding a heme-pentapeptide with increased solubility in aqueous solvents and a 1–2 order of magnitude higher stability of the monomeric state relative to canonical microperoxidases. The electronic spectra in the near-UV and visible regions have been studied as a function of MMP-5 concentration and pH. The spectroscopic properties of MMP-5 are typical of microperoxidases with high-spin hexa- or pentacoordinate heme species dominant in the 1–8 pH range and low-spin states prevailing at higher pH values. In the presence of hydrogen peroxide, MMP-5 displays peroxidatic activities towards several compounds.