Efficient proton shuttle makes SazCA an excellent CO2 hydration enzyme

The fastest member of the carbonic anhydrase family catalysing the reversible hydration of carbon dioxide to bicarbonate ions has been recently reported to be SazCA. While thermostable, this enzyme shows exceptional activity at 353 K for the reaction. This study explores the molecular basis for the exceptional activity of SazCA, in contrast to SspCA, probed using molecular dynamics simulations. Our simulations, carried out at different temperatures, indicate the presence of efficient proton shuttle between the active zinc centre and His64 residue in the two enzymes. The proton accepting His64 residue was identified to have in and out conformations with the in conformations being supportive to proton acceptance. Our simulations show a large population of in conformations in SazCA making the enzyme exhibit an exceptional activity. The RMSF and H-bonds analysis confirmed the role of His2 and His207 in supporting the attainment of in conformations in SazCA resulting in exceptional activity. Communicated by Ramaswamy H. Sarma

Automated summary

The fastest member of carbonic anhydrase family, SazCA, has been reported to exhibit exceptional activity in the reversible hydration reaction of carbon dioxide. This study explores the molecular basis for the difference in activity between SazCA and SspCA using molecular dynamics simulations. Our simulations reveal the presence of efficient proton shuttle between the active zinc center and His64 residue in both enzymes. However, SazCA shows a larger population of conformation favoring proton acceptance, leading to its exceptional activity.