Vera Engelbrecht and Thomas Happe made a significant step toward understanding the evolution of green algae. Credit: ©RUB, Marquard

Anew jigsaw piece in the evolution of green algae has been identified by researchers at Ruhr-Universität Bochum, together with colleagues from Max Planck Institute in Mülheim an der Ruhr, in Germany. They analyzed the hydrogen-producing enzyme of a phylogenetically old alga. The team, headed by Vera Engelbrecht and Prof Dr. Thomas Happe from the research group Photobiotechnology, in Bochum, outlined their results in the journal “Biochimica et Biophysica Acta.”

Hydrogen-producing enzymes, so-called hydrogenases, have originally occurred in numerous bacteria. Green algae, too, contain such enzymes, using them for the light-driven generation of hydrogen. “The origins of this enzyme in algae had long been a mystery,” says Vera Engelbrecht. “We have now analyzed a link in evolutionary history of hydrogenases that had previously been missing.”

Algae, which are relatively young in evolutionary terms, contain specialized hydrogenases that show significant differences to the original varieties in bacteria. They are smaller and have a specific surface used for docking to the cell’s photosynthesis machinery. To this end, they bind to ferredoxin, a molecule that mediates electron transfer. Thus, they are able to produce hydrogen using light energy.

The phylogenetically old alga Chlorella variabilis has likewise the ability for light-driven generation of hydrogen. The researchers from Bochum and Mülheim isolated and characterized the Chlorella hydrogenase. Unlike in young algae, it shares many characteristics with the original bacteria enzyme and is unable to bind to the electron carrier ferredoxin.

“We found the results surprising,” said Dr. Happe. “Chlorella appears to still have an original metabolic pathway, which has changed completely in phylogenetically younger algae.”

The question why the more recent algae have developed a specialized hydrogenase in order to dock to photosynthesis via ferredoxin remains to be answered. “We are currently attempting to identify the precise metabolic connection of chlorella hydrogenase and to detect photosynthetic protein complexes in the organism that are as yet unknown,” says Dr. Happe.

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