One isoform for one task? The second hydrogenase of Chlamydomonas reinhardtii prefers hydrogen uptake

摘要

Gaining knowledge about the algal hydrogen metabolism is prerequisite for the biotechnological exploitation of photosynthetic H-2 production. Model organism Chlamydomonas reinhardtii encodes two [FeFe]-hydrogenases, which are individually capable of catalysing the reversible reduction of protons to molecular hydrogen. While physiological results indicated that HYDA1, connected to the photosynthetic electron transfer pathway via plant-type ferredoxin PETF, is accountable for a major part of algal H-2 evolution, the role of HYDA2 in the algal metabolism is not understood yet. Herein, a comprehensive screening of enzymatic attributes was conducted, revealing that the two enzymes differ in their affinity to oxidised PETF. Notably, utilising protein film voltammetry, a higher catalytic preference of HYDA2 to consume H-2 was observed. Site directed exchange mutagenesis revealed the contribution of a hydroxyl group in place of threonine 226, present in HYDA1, but not in HYDA2, potentially influencing the electronic properties of the active site, thereby fine-tuning catalytic function. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.