Structure and function relationships in enzymes.

Our research is aimed at understanding the structure-function relationships in pharmacologically important enzymes. Currently, we are involved in studying the human glutathione-dependent formaldehyde dehydrogenase (FDH), a member of the alcohol dehydrogenase family. FDH, also known as Class III alcohol dehydrogenase catalyzes the oxidation and reduction of glutathione adducts, S-hydroxymethylglutathione and S-nitrosoglutathione more efficiently than primary alcohols and aldehydes. This substrate specificity and the random kinetic mechanism of FDH are in contrast to the predominantly ordered mechanism of extensively studied Class I alcohol dehydrogenases in spite of being very similar structurally. Our structural studies on FDH also show the presence of a unique process not observed so far, in the catalytic pathway of other vertebrate alcohol dehydrogenases. FDH-binary and ternary complexes show that the active site zinc, which plays a crucial role in the catalysis, moves back and forth between two positions during the catalytic cycle of FDH. While in one of its position, zinc interacts directly with the alcohol substrate and promotes catalysis, in its other position, zinc is displaced by more than 2 Å away from the substrate, thereby diminishing the strength of their interaction. We are taking crystallographic and stopped-flow kinetic approaches to understand the structural basis of the random kinetic mechanism of FDH and the significance of zinc movement in its catalytic pathway.

Carboxylesterase, Glutathione Dependent Formaldehyde Dehydrogenase, Structure-activity Relationships
biochemistry & molecular biology