Improving the unnatural and promiscuous nitroaldolase activity of modern and ancestral HNLs

Abstract

Enzymes in superfamilies such as the α/β-hydrolase fold superfamily have similar structures and active sites because they evolved from a common ancestor. Since enzymes within a superfamily catalyze different reactions, the common ancestor may have been a promiscuous catalyst. Our hypothesis is that promiscuous ancestral enzymes may be better starting points to obtain new catalytic activities compared to modern enzymes. To test this hypothesis, I tried to improve the promiscuous and unnatural nitroaldol activity in both a modern and an ancestral hydroxynitrile lyase using semi rational and random approaches. My results showed that the ancestral enzyme was not a better starting point compared to the modern enzyme after the modern enzyme was stabilized by a single mutation.