Hydrogen Oxidation by Clostridium kluyveri

Stephen C Kinsky

doi:10.1016/s0021-9258(18)70214-7

Stephen C Kinsky

Open Access

https://doi.org/10.1016/s0021-9258(18)70214-7

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Abstract

&urn kluyveri were capable of reducing pyridine nucleotides with hydrogen. Subsequent investigations have shown that a heatstable cofactor of undetermined nature present in boiled cell extracts was required (2). Pyridine nucleotide reduction with hydrogen has since been demonstrated in a number of other microorganisms (3-5). The present study was undertaken to explore in greater detail the alternative routes of hydrogen oxidation in C. kluyveri. Particular attention was paid to a comparison of the requirements for pyridine nucleotide, flavin nucleotide, and dye reduction, The available data suggest that the unknown cofactor does not function in the activation of hydrogen but acts between an activated hydrogen intermediate and pyridine nucleotide. Additional evidence is also presented showing that more than one enzyme is required for pyridine nucleotide reduction with hydrogen. A preliminary report of these results has been published (6).

Highlights

Triphenyl tetrazolium was employed in the present study, similar results have been obtained with benzyl viologen, Safranin 0, indigo disulfonate, methylene blue, and indophenol
The present investigation of hydrogen oxidation by C. kluyveri has suggested the following main points. (a) Flavin reduction does not require the participation of a heat stable cofactor which is necessary for pyridine nucleotide reduction
(6) The cofactor probably functions as an electron carrier between an activated hydrogen intermediate and DPN because it can be replaced by benzyl viologen and Safranin 0. (c) FAD is partially effective in substituting for the cofactor. (d) At least two enzymes are involved in pyridine nucleotide reduction. (e) An enzyme not required for dye or flavin reduction is necessary for DPN reduction

Summary

RESULTS

Prepared extracts of C. kluyveri catalyze the reduction of pyridine nucleotides by hydrogen.’ Anaerobic dialysis of the. In the presence of boiled cell extract almost all the added pyruvate was reduced within 30 minutes and the rate remained essentially linear. Addition of DPN is required for masima pyruvate reduction and the appreciable pyruvate disappearance observed in the absence of added DPN is due to the large amounts of the latter present in the boiled cell extract. Repeated attempts to show a cofactor or DPN requirement for dye reduction have been consistently negative The significance of these results will be discussed subsequently. This is analogous to the situation observed with dyes and it should be noted that, in all cases in which dye and flavin reduction were compared, qualitatively similar results have been obtained.

IO 12 14 16 18

IIII I

DISCUSSION

SUMMARY