Carbonyl sulfide hydrolase (EC3.13.1.7; abbreviated as COSase) is an enzyme that degrades carbonyl sulfide (COS) to hydrogen sulfide (H2S) and carbon dioxide (CO2). Isolated from Thiobacillus thioparus bacterium, the potential of COSase would reduce the high global warming effect of COS and change the ozone chemistry, because COS is the source of sulfur in the troposphere.[1][2][3]
Being that it is a hydrolase, which is an enzyme that uses water to break chemical bonds, the name suggests that within the mechanism are water molecules that are involved in disseminating molecules within the reaction. The very name when broken down means that it is an enzyme that breaks down carbonyl sulfide.
History
COSase was isolated, characterized and structure was determined from Thiobacillus thioparus bacterium. In search for a chemical method to break down COS more efficiently than the biologically established methods that employ the soil environment for degradation enzymes. These enzymes are carbonic anhydrase, carbonic disulfide hydrolase, nitrogenase, carbon monoxide, and RuBisCO.[4][5][6][7][8][9][10][11][12] The enzymes listed are limited in their use due to specificities and optimal environments, which is why chemical development of an enzyme unique to catalyzing the degradation of COS is researched. - Thiobacillus thioparus is a bacterium found both in soil and freshwater and is known for its sulfur-oxidizing properties. The strain used to create COSase is THI11, which was originally isolated as a thiocyanate degrading microorganism.[13] The enzyme was found by putting the extract of T. thioparus strain THI115 through column chromatography to purify it and ICP-MS to deduce the structure.[1]
Structure
Using sodium dodecyl sulfate–polyacrylamide gel electrophoresis, a subunit molecular mass of 27 kDa was found.[1] After testing for expression in E. coli the true molecular mass of ~94 kDa was found by SEC-MALS.[1]ICP-MS shows that there is one zinc ion per sub unit.[1] 35 amino acid sequence found on the N-terminal: MEKSNTDALLENNRLYAGGQATHRPGHPGMQPIQP.[1] There are five strands (β1−β5) that make up β-sheet core and four α-helices (α1, α2, α3, and α6) in its flank, with two additional helices (α4 and α5) that protrude from its core. They arrange in homodimer pairs to form ten-stranded β-sheets.[1] Between two subunits of a homodimer is the catalytic site. Cys44, His97, Cys 100, and a water molecule coordinate with a zinc ion, with a thiocyanate molecule in the catalytic site pocket.[1]
Function
COSase is responsible for the degradation of COS to H2S and CO2 in the second step of SCN− assimilation. It hydrolyzes COS with a certain specificity over a wide range of concentrations both in vivo and in vitro.[1]
Hydroxide and zinc io ns perform a nucleophilic attack on the carbon in the COS molecule, which creates an intermediate with zinc bound to hydroxide oxygen and sulfur of the COS molecule. Oxygen is then released from zinc and forms CO2. Water from the solvent interacts with the su lfur-zinc ion and regenerates the active site and releases H2S.[1]
1 2 3 4 5 6 7 8 9 10 11 Ogawa T, Noguchi K, Saito M, Nagahata Y, Kato H, Ohtaki A, etal. (March 2013). "Carbonyl sulfide hydrolase from Thiobacillus thioparus strain THI115 is one of the β-carbonic anhydrase family enzymes". Journal of the American Chemical Society. 135 (10): 3818–25. Bibcode:2013JAChS.135.3818O. doi:10.1021/ja307735e. PMID23406161.
↑ Chin M, Davis DD (1995). "A reanalysis of carbonyl sulfide as a source of stratospheric background sulfur aerosol". Journal of Geophysical Research. 100 (D5): 8993–9005. Bibcode:1995JGR...100.8993C. doi:10.1029/95JD00275.
↑ Andreae MO (16 May 1997). "Atmospheric Aerosols: Biogeochemical Sources and Role in Atmospheric Chemistry". Science. 276 (5315): 1052–1058. doi:10.1126/science.276.5315.1052.
↑ Supuran CT (February 2008). "Carbonic anhydrases: novel therapeutic applications for inhibitors and activators". Nature Reviews. Drug Discovery. 7 (2): 168–81. doi:10.1038/nrd2467. PMID18167490. S2CID3833178.
↑ Seefeldt LC, Rasche ME, Ensign SA (April 1995). "Carbonyl sulfide and carbon dioxide as new substrates, and carbon disulfide as a new inhibitor, of nitrogenase". Biochemistry. 34 (16): 5382–9. doi:10.1021/bi00016a009. PMID7727396.
↑ Protoschill-Krebs G, Wilhelm C, Kesselmeier J (September 1996). "Consumption of carbonyl sulphide (COS) by higher plant carbonic anhydrase (CA)". Atmospheric Environment. 30 (18): 3151–3156. Bibcode:1996AtmEn..30.3151P. doi:10.1016/1352-2310(96)00026-X.
↑ Haritos VS, Dojchinov G (January 2005). "Carbonic anhydrase metabolism is a key factor in the toxicity of CO2 and COS but not CS2 toward the flour beetle Tribolium castaneum [Coleoptera: Tenebrionidae]". Comparative Biochemistry and Physiology. Toxicology & Pharmacology. 140 (1): 139–47. doi:10.1016/j.cca.2005.01.012. PMID15792633.
↑ Ensign SA (April 1995). "Reactivity of carbon monoxide dehydrogenase from Rhodospirillum rubrum with carbon dioxide, carbonyl sulfide, and carbon disulfide". Biochemistry. 34 (16): 5372–8. doi:10.1021/bi00016a008. PMID7727395.
↑ Alterio V, Di Fiore A, D'Ambrosio K, Supuran CT, De Simone G (August 2012). "Multiple binding modes of inhibitors to carbonic anhydrases: how to design specific drugs targeting 15 different isoforms?". Chemical Reviews. 112 (8): 4421–68. doi:10.1021/cr200176r. hdl:2158/776392. PMID22607219.
↑ Zhao S, Yi H, Tang X, Kang D, Yu Q, Gao F, Wang J, Huang Y, Yang Z (1 February 2018). "Mechanism of activity enhancement of the Ni based hydrotalcite-derived materials in carbonyl sulfide removal". Materials Chemistry and Physics. 205: 35–43. doi:10.1016/j.matchemphys.2017.11.002.
Piazzetta P, Marino T, Russo N (June 2015). "The working mechanism of the β-carbonic anhydrase degrading carbonyl sulphide (COSase): a theoretical study". Physical Chemistry Chemical Physics. 17 (22): 14843–8. Bibcode:2015PCCP...1714843P. doi:10.1039/C4CP05975A. PMID25980540.
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