Ancestral nucleotide cofactor-dependent enzymes: emergence of catalysis and functional divergence

MASCOTTI, MARÍA LAURA

Simposio; oLife Annual Meeting 2022; 2022

Nucleotide-dependentenzymes are key assets for life. They are involved in cellular processes asrespiration, detoxification, redox homeostasis, defense, etc. These enzymesstand out from the others because of two reasons: (i) they enable catalysis bythe orchestrated action of a variety of elements –an electron donor or acceptor,a substrate, and the amino acids forming the catalytic network at the active site-and, (ii) nucleotides are considered relics from the pre-biotic world, which werelikely the drivers of the transition from chemical catalysis to enzymaticcatalysis, a major contribution for life emergence on Earth. One of the majorgroups of extant, nucleotide-based cofactors are the flavin cofactors. In thiswork, different kinds of flavin-dependent enzymes, that are alleged to bepresent in the last universal common ancestor (LUCA), have been investigatedfrom an evolutionary biochemistry perspective. Ancestral sequencereconstruction was carried out on the phylogenies of selected families and theancestors at the major divergence points, in terms of functionality ortaxonomic distribution, were selected for experimental characterization. Thiswork allowed us to understand some of the specific biochemical aspects of eachselected protein family, but also to make broader conclusions on how catalysisis built up through evolution in flavin-dependent enzymes. It has revealed thatthe molecular mechanism dictating the type of enzyme function seems to beepistasis involving the cofactor. This means that the catalytic network isformed by historical substitutions distantly located in the active site of theenzyme which only act together synergistically by the direct interaction withthe nucleotide cofactor(s) molecule(s). Such insights help in understanding howenzymes have evolved to fulfill a plethora of roles in nature as biocatalysts.