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Redox Potentials of Certain Vitamins K: Implications for a Role in Sulfite Reduction by Obligately Anaerobic Bacteria

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  • Biological Sciences: Biochemistry


Redox potentials of a menaquinone (MK-6), isolated in earlier researches from two species of the obligately anaerobic genus, Desulfovibrio, as well as two other vitamins K2—menaquinones (MK-5) and (MK-9)— have been determined polarographically. The measurements have been validated by determination of redox potentials of 1,4-naphthoquinone and vitamin K1 which agree with published potentiometric values. Em7 for menaquinone (MK-6) is -0.067 ± 0.010 V. Redox potentials calculated for terminal acceptor couples currently proposed in the mechanisms of sulfate reduction by Desulfovibrio are consistent with the involvement of menaquinone (MK-6) in at least one of the steps postulated during electron transfer with ultimate production of sulfide.

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