Carbonic Anhydrase IX/CA9 His

The CAIX works as a dimeric molecule composed of two monomeric proteins liked with a disulfide bond between cysteine residues of the two CAIX monomers, while the structure of CAXII is stabilized by 19 hydrogen-bonded interactions in the dimer interface. Carbonic anhydrases IX and CAXII (CAIX/CAXII) are transmembrane zinc metalloproteins that catalyze a very basic but crucial physiological reaction: the conversion of carbon dioxide into bicarbonate with a release of the proton.CAIX functions with bicarbonate transporters (including electroneutral bicarbonate transporter NBCn1 (SLC4A7)) to bring in HCO3- produced in a CAIX-mediated hydration reaction of CO2, and amino acid transporters (including the large neutral amino acid transporter 1 (LAT1) and CD98 heavy chain (CD98hc)) to transport in essential amino acids and glutamine (via interaction with glutamine transporter SLC1A5 and sodium-coupled neutral amino acid transporter 2 (SNAT2) facilitating the uptake of aminoacid by SLC1A5), which cancer cells employ as an alternative metabolic energy source and biosynthetic precursor. CAIX also creates unique interactions with collagen- and laminin-binding integrins at the leading edge of migrating cells.