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INVESTIGADORES

GONZALEZ Javier Marcelo

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Título:

Structure and function of extremophilic enzymes for engineering carbon fixation and assimilation

Autor/es:

JAVIER MARCELO GONZALEZ

Lugar:

Buenos Aires

Reunión:

Workshop; Colloquium de la Alexander von Humboldt Foundation; 2018

Institución organizadora:

Alexander von Humboldt Foundation

Resumen:

Structure and function of extremophilic enzymes for engineering carbon FIXATIONAND ASSIMILATIONSustainable biomass production entailsthe usage of energy from renewable sources to drive carbon fixation and delivervalue added chemicals. Oxygenic photosynthesis constitutes a natural example ofsuch process: plants, algae, and cyanobacteria use sunlight to split water intoO2 and reducing power, required for CO2 conversion intosugars. This process is responsible for the absorption of 440 Gt of CO2and emission of 300 Gt of O2 each year, essentially enabling life onEarth as we know it. Strikingly, the central metabolic pathway ofphotosynthesis?the Calvin-Benson-Basham (CBB) cycle?relies on a sluggish enzymecalled RuBisCO to catalyze the carboxylation step where CO2 entersthe CBB cycle. Indeed, this enzyme can fix carbon at a rate of only 3-10molecules of CO2 per second, which is 10-100 times slower than analogouscarboxylases. Furthermore, RuBisCO can confuse CO2 with O2,requiring an additional pathway to recycle the oxidized substrate and keep theCBB cycle running. This extra route releases some of the fixed CO2 therebydropping the photosynthesis yield as much as 30 %.Certainly, there is room to improve thecatalytic efficiency of RuBisCO, and probably that of CO2 fixationin general. Yet, natural evolution of RuBisCO in higher eukaryotes seems tohave reached a limit a long time ago, since they developed adaptations tocompensate for its poor catalytic activity. In contrast, photosyntheticmicrobes evolved pathways and enzymes to perform CO2 fixation in themost unlikely environments, which could replace or complement photosynthesis inhigher eukaryotes. In this regard, our recently established research group inSantiago del Estero aims to develop strategies to improve carbon fixation andassimilation by exploiting the genetic diversity of local extremophilic microorganisms.The collection of metabolic enzymes enabling proliferation of extremophiles inniches with extremes of pH, salinity, temperature, and/or UV radiation,constitutes a genetic pool ofenormous biotechnological value. We sampled briny waters in northwesternArgentina, including high altitude lakes in the Atacama Plateau of Catamarca (~4500 m above sea level), and the saline mudflats of Salinas de Ambargasta insouthwestern Santiago del Estero, in search for DNA for metagenomic analysis. Cloning,expression and structure-functional characterization of extremophilic enzymesinvolved in carbon fixation and assimilation will supply our enzyme toolbox formetabolic engineering, enabling new developments for synthetic carbonmetabolism. Besides, the resolution of these enzymes structures through X-raycrystallography will leverage our protein engineering efforts, enabling enzymeoptimization through directed evolution and rational enzyme design.

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