CA XIII

CA XIII is a cytosolic carbonic anhydrase isozyme that catalyzes CO2 hydration and is expressed in several normal tissues[1]. Mechanistically, recombinant mouse CA XIII showed catalytic activity similar to mitochondrial CA V and cytosolic CA I, supporting its role in physiological acid-base processes[1]. In colorectal mucosa, CA XIII expression is down-regulated in tumor cells compared with normal tissue, and the lowest signal was detected in carcinoma samples[2]. Compared with related cytosolic isoforms, CA XIII showed a unique and widespread distribution pattern distinct from CA I, CA II, and CA III[1]. Structurally, human CA XIII has high similarity to cytosolic isozymes but active-site differences support isozyme-specific inhibitor design[3]. For experimental applications, CA XIII is efficiently inhibited by sulfonamide inhibitors, including acetazolamide, while intrinsic thermodynamic studies support structure-activity analysis of CA XIII inhibitor binding[1][4].