Ancient bile enzymes (OYEs) were discovered in the 1930s and have been the subject of much research ever since. This is because these biocatalysts – colored yellow by a helper molecule – are capable of carrying out reactions of great value to the chemical industry, such as the production of drug precursors or perfumes. Although OYE is found in many organisms, its natural role for these organisms is not yet understood — perhaps because the focus of research has been on their biotechnological applications. Researchers led by Associate Professor Dr Anja Heimsheimer and Professor Thomas Häppe from Ruhr-University Bochum, Germany, have now shown that OYE from the unicellular green alga Chlamydomonas reinhardtii is vital for this plant microorganism to protect itself from photostress.
OYEs in microalgae use energy from photosynthesis
“Our research group is among the first to investigate OYEs in algae,” says Dr. Stephanie Bohmer, lead author of the study. “Initially, we set out to determine if these biocatalysts were also suitable for industrial processes. We were particularly interested in whether microalgae could use the energy of photosynthesis to drive the relevant chemical reactions. This could help create more environmentally friendly products.” ” Researchers can already prove this: a chemical molecule added to living algae cells only converted at high rates in light. “This result also indicates that the so-called algal reductase responsible for this conversion is related to photosynthesis,” says Boehmer. Therefore, researchers from the Photobiotechnology Working Group investigated how an algal strain in which an OYE biocatalyst is defective would adapt to strong light.
Excess light energy must be dissipated
In collaboration with researchers from the University of Leipzig, the Bochum research team has already been able to show that this algal strain is barely able to dissipate excess light energy. “Photosynthetic organisms such as algae and plants must always maintain a balance between absorbing light energy and converting it into chemical energy,” explains Anja Hemschemeier, who led the study. “Otherwise, oxidative cell damage would occur if the light was too strong. Therefore, these organisms have sophisticated protection mechanisms in place to dissipate excess light energy, for example heat.”
In the microalgae strain lacking OYE, the researchers detected none of these protective mechanisms at all, and thus the strain showed oxidative damage. “We suspect that a specific molecule, which is normally converted by this biocatalyst in algal cells, is essential for the homeostasis of photosynthesis,” Hemschemeier says.
The research team now plans to get to the bottom of the matter. “Photosynthetic organisms provide a foundation for our life. It’s very important to understand how they adapt to stress, and we think we’ve found another piece of the jigsaw here,” Hemschemeier concludes.