Abstract
Corrinoid-deficientPropionibacterium freudenreichii subsp. shermanii showed adenosylcobalamin-(AdoCb1)-independent ribonucleotide reductase (RNR) activity in the presence of air. Increasing the incubation time with free access of O2 led to an increase in RNR activity. As polarographic estiamtions of O2 uptake demonstrated, AdoCb1-independent RNR activity (with ADP as substrate) in a cell-free system of corrinoid-deficientP. freudenreichii was accompanied by specific molecular oxygen consumption. The activity was not inhibited by carbonyl cyanidem-chlorophenylhydrazone (CCCP) or carbonyl cyanidep-(trifluoromethoxy)phenylhydrazone (FCCCP). The activity was present in the cytoplasmic membrane-free soluble fraction of the cell extract, and it was inhibited by hydroxyurea. Manganese ions were important for the cell division of corrinoid-deficientP. freudenreichii and stimulated RNR activity after 8-hydroxyquinoline or EDTA treatment of the cell extract. We therefore concluded thatP. freudenreichii is able to form DNA (deoxyribosylic precursors) using AdoCb1-dependent ribonucleotide reductase and also with an alternative AdoCb1-independent molecular-oxygen-consuming RNR system.
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