[Mn]-hydrogenase: A new step towards redesigning hydrogenases

First functional [Mn]-hydrogenase successfully engineered

June 03, 2019
Hydrogen gas (H2) is proposed as a clean energy carrier for the future world - as long as its production works without the use of fossil fuels. Accordingly, there is intensive research on hydrogenases, enzymes that catalyze H2 production and consumption. Now scientists from MPI’s Shima group in cooperation with scientists from Lausanne were able to construct an active semisynthetic [Mn]-hydrogenase, thus providing a new way for designing and building new robust and efficient H2-activtion catalysts that might take part in future technologies.

Hydrogenases are widely spread in nature. For the metal ion in the active center, nature obviously chooses only Fe or Ni, respectively, as in [NiFe]-, [FeFe]-, and [Fe]-hydrogenases.

Fig 1.: The strategy for constructing the semisynthetic [Mn]-hydrogenase.  

As Xile Hu, head of the Laboratory of Inorganic Synthesis and Catalysis at EPFL in Lausanne and cooperation partner of Seigo Shima, notes: “One wonders why nature does not choose other metals for the active center of hydrogenases. Is it purely due to bioavailability? Probably not, since metalloenzymes containing molybdenum, manganese, cobalt, and copper are pretty common.” Although synthetic chemists have synthesized many metal complexes which catalyze H2 cleavage, to date none of these semi-synthetic hydrogenases were active unless they were constructed by using the native metals (Ni and Fe). A recent report has shown that ruthenium (Ru), which is more active than Fe in synthetic H2 activation, fails to construct an active hydrogenase.

Fig. 2: The semisynthetic [Mn]-hydrogenase catalyzes H2 activation and hydride transfer. The protein structure was modeled based on the crystal structure of [Fe]-hydrogenase from Methanocaldococcus jannaschii.

In cooperation with Xile Hu’s lab, the Seigo Shima group at the Max Plank Institute for Terrestrial Microbiology has successfully constructed a [Mn]-hydrogenase using a Mn model complex and the apoenzyme of [Fe]-hydrogenase (Fig. 1), which is active in H2-activation and hydride transfer. “This is the first functional hydrogenase that contains a non-native metal ion”, Max-Planck scientist Seigo Shima explains. “With further biotechnological improvements, this semisynthetic [Mn]-hydrogenase has the potential to reveal an even higher catalytic activity than the native [Fe]-hydrogenase.”

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