title: Mutation of active site residues Asn67 to Ile, Gln92 to Val and Leu204 to Ser in human carbonic anhydrase II: influences on the catalytic activity and affinity for inhibitors.
abstract: Site-directed mutagenesis has been used to change three amino acid residues involved in the binding of inhibitors (Asn67Ile; Gln92Val and Leu204Ser) within the active site of human carbonic anhydrase (CA, EC 4.2.1.1) II (hCA II). Residues 67, 92 and 204 were changed from hydrophobic to hydrophilic ones, and vice versa. The Asn67Ile and Leu204Ser mutants showed similar k(cat)/K(M) values compared to the wild type (wt) enzyme, whereas the Gln92Val mutant was around 30% less active as a catalyst for CO(2) hydration to bicarbonate compared to the wt protein. Affinity for sulfonamides/sulfamates was decreased in all three mutants compared to wt hCA II. The effect was stronger for the Asn67Ile mutant (the closest residue to the zinc ion), followed by the Gln92Val mutant (residue situated in the middle of the active site) and weakest for the Leu204Ser mutant, an amino acid situated far away from the catalytic metal ion, at the entrance of the cavity. This study shows that small perturbations within the active site architecture have influences on the catalytic efficiency but dramatically change affinity for inhibitors among the CA enzymes, especially when the mutated amino acid residues are nearby the catalytic metal ion.
authors.affiliation: Balıkesir University, Faculty of Science and Literature, Department of Biology, Balıkesir, Turkey.
authors.forename: Sumeyye
authors.initials: S
authors.lastname: Turkoglu
authors.forename: Alfonso
authors.initials: A
authors.lastname: Maresca
authors.forename: Meltem
authors.initials: M
authors.lastname: Alper
authors.forename: Feray
authors.initials: F
authors.lastname: Kockar
authors.forename: Semra
authors.initials: S
authors.lastname: Işık
authors.forename: Selma
authors.initials: S
authors.lastname: Sinan
authors.forename: Ozen
authors.initials: O
authors.lastname: Ozensoy
authors.forename: Oktay
authors.initials: O
authors.lastname: Arslan
authors.forename: Claudiu T
authors.initials: CT
authors.lastname: Supuran
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D024402:Carbonic Anhydrase II / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D002257:Carbonic Anhydrase Inhibitors / Q000737:chemistry*; D002256:Carbonic Anhydrases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020134:Catalytic Domain; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D013449:Sulfonamides / Q000138:chemical synthesis / Q000737:chemistry
chemical_list: D002257:Carbonic Anhydrase Inhibitors; D013449:Sulfonamides; D024402:Carbonic Anhydrase II; D002256:Carbonic Anhydrases