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Special Seminar - Prof. Tony Dean

University of Minnesota

The evolution of two catalytic mechanisms

Biochemistry Seminar Room 231
Jun. 30, 2017
  • 12:00

I will discuss the evolution of two catalytic mechanisms. In the first, two homologous enzymes deploy the same catalytic machinery to stabilize different transition states. In the second, two homologous enzymes stabilize distinct transition states while carrying out the same overall chemical transformation.

1) The means by which superfamilies of specialized enzymes arise by gene duplication and functional divergence are poorly understood. I show how reconstructing ancestral enzymes can be used to distinguish between hypotheses of gene duplication and functional divergence using the emergence of plant hydroxynitrile lyases (HNLs) from plant esterases as an exemplar. I will argue that the chemical properties of the catalytic machinery remained essentially unchanged. Instead, the evolutionary positioning of the substrates in the active site, together with the chemistries inherent to the substrate structures, were critical to the evolution of catalysis. 

2) An active site lysine essential to catalysis in isocitrate dehydrogenase (IDH) is absent from related enzymes. As all family members catalyze the same oxidative beta-decarboxylation at the 2R-malate core common to their substrates, it seems odd that an amino acid essential to one is not found in all. I will discuss the role of this lysine in transition state stabilization and why it is needed in isocitrate dehydrogenase but in not other related enzymes.