A critical feature that drives tumorigenesis is metabolic reprogramming. One important example includes the reductive carboxylation of glutamine, which requires the activity of isocitrate dehydrogenase 1 (IDH1). Under hypoxia and acidic pH, the reverse reaction, the NADPH-dependent reduction of a-KG to form isocitrate, plays a critical role in driving the reductive metabolism of glutamine to fuel tumorigenesis. The molecular mechanisms behind the increased rates of isocitrate production by IDH1 at acidic pH are not yet understood. We seek to establish the molecular mechanisms of IDH1 catalysis and identify the structural and microenvironmental features that support the reverse reaction. We hypothesize there are key pH-sensing residues that result in increased rates of IDH1 activity at low pH to drive reductive metabolism. Such pH sensors can play an important role in regulating activity upon a change in pH. To test if this residue affects rates of catalysis under varying pH, we designed E304L and E304K IDH1 mutants. We show that the E304K mutation has similar catalytic efficiency in the forward direction compared to wild type IDH1, and studies on the reverse reaction is underway. We have designed a computational model mimicking the normal activity of IDH1. We will further modify the model to predict catalysis at different pH, so we can infer the relations between the pH sensing residues in IDH1 activity. By understanding the structural mechanics of IDH1 activity as a function of pH via computational methods and experimental data, we will better understand the role of reductive metabolism in cancer.

Molecular mechanisms in pH dependency of isocitrate dehydrogenase I (idh1) activity

2019 Spring National Meeting

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