- Mahon BP, Bhatt A, Socorro L, Driscoll JM, Okoh C, Lomelino CL, Mboge MY, Kurian JJ, Tu C, Agbandje-McKenna M, Frost SC, McKenna R
- Structure of carbonic anhydrase IX is adapted for low pH catalysis.
- Biochemistry. 2016 Jul 20.
- Human carbonic anhydrase IX (hCA IX) expression in many cancers is associated with hypoxic tumors and poor patient outcome. Inhibitors of hCA IX have been used as anti-cancer agents with some entering Phase I clinical trials. hCA IX is a transmembrane protein whose catalytic domain faces the extracellular tumor milieu, which is typically associated with an acidic microenvironment. Here, we show that the catalytic domain of hCA IX (hCA IX-c) exhibits the necessary biochemical/biophysical properties that allow for low pH stability and activity. Furthermore, the unfolding process of hCA IX-c appears to be reversible and its catalytic efficiency is suggested to be correlated directly with its stability between 3.08.0. To rationalize this, we determined the X-ray crystal structure of hCA IX-c to 1.6 A resolution. Insights from this study suggest an understanding of hCA IX-c stability and activity in low pH tumor microenvironments, and may be applicable to determining pH-related effects on other enzymes.