PMID: 27439028
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.