Does anybody know how is PQQH2 (reduced pyrroloquinoline quinone), formed by membrane bound glucose dehydrogenase in bacteria during glucose oxidation, oxidized back to PQQ? What happens with hydrogen then? Any literature on this topic specifically for bacteria? Thank you!
Ahoj Pavle (= "Hi, Pavel" in Czech), the recycling of PQQH2 back to PQQ is spontaneous and coupled (via proton transfer) with the reduction of reactive oxygen species . . . hence the potential antioxidative effect of PQQH2.
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Mukai et al. (2015) Biosci Biotechnol Biochem 80: 178-187.
https://www.ncbi.nlm.nih.gov/pubmed/26264520
Ahoj Martine! (Hi Martin!:) Thanks. Yep, I came across this paper. The antioxidant hypothesis makes sense, but it is based on in vitro assays in this study. I am still looking for other alternative functions of PQQH2 in bacteria. Any suggestions welcome.
If oxygen is present, it will react readily with PQQH2, with PQQ and hydrogen peroxide as the products. (PQQ is, therefore, potentially, and so typically, a double-edged sword.) i would expect a close coupling between the hydrogen peroxide production and its decomposition to water and molecular oxygen by catalase.
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