title: Anion inhibition study of the β-carbonic anhydrase (CahB1) from the cyanobacterium Coleofasciculus chthonoplastes (ex-Microcoleus chthonoplastes).
abstract: We investigated the catalytic activity and inhibition of the β-class carbonic anhydrase (CA, EC 4.2.1.1) CahB1, from the relict cyanobacterium Coleofasciculus chthonoplastes (previously denominated Microcoleus chthonoplastes). The enzyme showed good activity as a catalyst for the CO2 hydration, with a kcat of 2.4 × 10(5)s(-1) and a kcat/Km of 6.3 × 10(7)M(-1)s(-1). A range of inorganic anions and small molecules were investigated as inhibitors of CahB1. Perchlorate and tetrafluoroborate did not inhibit the enzyme (KIs >200 mM) whereas selenate and selenocyanide were ineffective inhibitors too, with KIs of 29.9-48.61 mM. The halides, pseudohalides, carbonate, bicarbonate, trithiocarbonate and a range of heavy metal ions-containing anions were submillimolar-millimolar inhibitors (KIs in the range of 0.15-0.90 mM). The best CahB1 inhibitors were N,N-diethyldithiocarbamate, sulfamate, sulfamide, phenylboronic acid and phenylarsonic acid, with KIs in the range of 8-75 μM, whereas acetazolamide inhibited the enzyme with a KI of 76 nM. This is the first kinetic and inhibition study of a cyanobacterial CA. As these enzymes are widespread in many cyanobacteria, being crucial for the carbon concentrating mechanism which assures substrate to RubisCO for the CO2 fixation by these organisms, a detailed kinetic/inhibition study may be essential for a better understanding of this superfamily of metalloenzymes and for potential biotechnological applications in biomimetic CO2 capture processes.
authors: Università degli Studi di Firenze, Dipartmento di Chimica Ugo Schiff, Via della Lastruccia 3, Rm. 188, 50019 Sesto Fiorentino (Florence), Italy.
authors: Daniela
authors: D
authors: Vullo
authors: K.A. Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya Str., Moscow 127276, Russia.
authors: Elena V
authors: EV
authors: Kupriyanova
authors: Università degli Studi di Firenze, Dipartmento di Chimica Ugo Schiff, Via della Lastruccia 3, Rm. 188, 50019 Sesto Fiorentino (Florence), Italy.
authors: Andrea
authors: A
authors: Scozzafava
authors: Istituto di Biochimica delle Proteine-CNR, Via P. Castellino 111, 80131 Napoli, Italy.
authors: Clemente
authors: C
authors: Capasso
authors: Università degli Studi di Firenze, Dipartmento di Chimica Ugo Schiff, Via della Lastruccia 3, Rm. 188, 50019 Sesto Fiorentino (Florence), Italy; Università degli Studi di Firenze, Neurofarba Dept., Section of Pharmaceutical and Nutriceutical Sciences, Via U. Schiff 6, 50019 Sesto Fiorentino (Florence), Italy. Electronic address: claudiu.supuran@unifi.it.
authors: Claudiu T
authors: CT
authors: Supuran
mesh_terms: D000595:Amino Acid Sequence; D000838:Anions / Q000737:chemistry*; D002257:Carbonic Anhydrase Inhibitors / Q000737:chemistry*; D002256:Carbonic Anhydrases / Q000737:chemistry*; D000458:Cyanobacteria / Q000378:metabolism*; D008969:Molecular Sequence Data
chemical_list: D000838:Anions; D002257:Carbonic Anhydrase Inhibitors; D002256:Carbonic Anhydrases
keywords: Anion; CO(2) capture; Carbon concentrating mechanism; Carbonic anhydrase; Cyanobacterium; Enzyme inhibitor; β-Class