A Streptococcus mutans superoxide dismutase that is active with either manganese or iron as a cofactor.

摘要: The superoxide dismutase produced by Streptococcus mutans OMZ176 during aerobic growth in a chemically defined medium (modified FMC) that was treated with Chelex 100 (to lower trace metal contamination) and supplemented high purity manganese purified (162-fold) heat treatment, ammonium sulfate precipitation, chromatofocusing chromatography. the same medium, but without iron, similarly (220-fold). molecular masses of each holoenzyme were approximately 43,000 subunit mass 20,700, indicating enzymes dimers two equally sized subunits. from manganese-grown cells enzyme (MnSOD) containing 1.2 atoms 0.25 iron/subunit. iron-grown an iron (FeSOD) 0.07 0.78 amino acid compositions MnSOD FeSOD virtually identical, their amino-terminal sequences identical through first 22 acids. Dialysis o-phenanthroline sodium ascorbate generated aposuperoxide 94% loss activity; subsequent dialysis apoenzyme either or ferrous reconstituted activity (recoveries 37 30%, respectively). Electrophoretic determination cytoplasmic radioiron distribution indicated (during growth) prevented insertion into dismutase, although levels at least other fractions not altered manganese. Therefore, S. used to form MnSOD, depending upon which available culture medium. Such "cambialistic" (those capable making cofactor substitution) may represent previously unrecognized family dismutases.