anhydrase

Anhydrase is a generic term for enzymes that catalyze reversible hydration or dehydration reactions of various substrates. The name is derived from the Greek words “anhydros” meaning “without water” and the enzyme suffix “ase”. These enzymes play key roles in biochemical pathways by facilitating the addition or removal of water molecules, thereby converting substrates between more or less hydrated forms.

The anhydrase superfamily is diverse, encompassing both metalloenzymes and non‑metal enzymes. A well‑known subgroup is the carbonic anhydrases (CAs), which are zinc‑containing enzymes that catalyze the interconversion of carbon dioxide and bicarbonate. These CAs are essential for acid‑base balance, respiration, and photosynthesis. Other members include oxaloacetate decarboxylase (also a water‑dependent enzyme), nitronate monooxygenases, and various dehydratases involved in carbohydrate metabolism.

Mechanistically, anhydrases often employ active‑site residues to stabilize charged transition states and coordinate metal ions that polarize water molecules. The catalytic cycle typically involves nucleophilic attack by a coordinated water dipole, leading to the removal of a proton and the transfer of a proton to a general base. In many metal‑based anhydrases, the metal ion (often Fe²⁺, Mn²⁺, or Zn²⁺) serves to activate the water molecule and stabilize the anionic intermediate.

Industrial and biomedical applications of anhydrases include therapeutic inhibitors for conditions such as glaucoma, altitude sickness, and epilepsy. In biotechnology, engineered anhydrases are used for bioconversion processes, carbon capture technologies, and biosensing devices. Despite the growing body of research, detailed structural information remains limited for many anhydrase family members, underscoring the need for continued biochemical and biophysical investigation.