Neutron crystallographic studies of carbonic anhydrase.

The carbonic anhydrases (CAs; EC 4.2.1.1) are a family of metalloenzymes that catalyze the reversible hydration of carbon dioxide (CO2) and bicarbonate (HCO3-). Since their discovery in 1933, CAs have been at the forefront of scientific discovery: the understanding of enzymatic reactions, structural biology, molecular dynamics, drug discovery, and clinical medicine. These ubiquitous enzymes equilibrate the reaction between CO2, HCO3-, and protons. Hence, CAs have important roles in ion transport, acid-base regulation, gas exchange, photosynthesis, and CO2 fixation. In this chapter, we describe the protocols leading to, and the analysis of CA neutron crystal structures. This accumulation of structural knowledge adds to our understanding of the enzymatic mechanism and development of CA inhibitors.