FAD and NAD(P)H-dependent coenzyme A disulfide/polysulfide reductases (CoADR/Psr) have been proposed to be important in the sulfur metabolism of the S0-reducing anaerobic hyperthermophiles Pyrococcusand Thermococcus. In these studies, we determined the structure for the FAD and coenzyme-A containing holoenzyme from P. horikoshii and characterized its substrate specificity. The enzyme is capable of reducing a variety of persulfide, disulfide, and polysulfide compounds. The results suggest that likely in vivo substrates are NAD(P)H and per and polysulfide derivatives of coenzyme-A, although the aerobic rapid recycling of persulfide substrate observed may explain findings that CoADR is non-essential for S0 respiration in Pyrococcus or Thermococcus and instead participates in oxidative defense in the presence of S0. One homologue of CoADR, Npsr, is usually found only  in mesophilic bacteria. We are currently characterizing the Npsr of the sulfate (but not sulfur) reducing Archaeoglobus fulgidus, the only Npsr found in archaea or hyperthermophiles to date.

Mechanisms of FAD and NAD(P)H-dependent persulfide and polysulfide reducing enzymes of Pyrococcus and Archaeoglobus

245th National Meeting (2013)

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