A Mechanistic Study of Carbonic Anhydrase Enhanced Calcite Dissolution

• Main Authors: Dong, Sijia, Berelson, William M., Teng, H. Henry, Rollins, Nick E., Pirbadian, Sahand, Elâ€Naggar, Mohamed Y., Adkins, Jess F.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: American Geophysical Union 2020
• Subjects: Adkins; Ocean acidification
• Online Access: https://doi.org/10.1029/2020gl089244

Carbonic anhydrase (CA) has been shown to promote calcite dissolution (Liu, 2001, https://doi.org/10.1111/j.1755-6724.2001.tb00531.x; Subhas et al., 2017, https://doi.org/10.1073/pnas.1703604114), and understanding the catalytic mechanism will facilitate our understanding of the oceanic alkalinity cycle. We use atomic force microscopy (AFM) to directly observe calcite dissolution in CAâ€bearing solution. CA is found to etch the calcite surface only when in extreme proximity (~1 nm) to the mineral. Subsequently, the CAâ€induced etch pits create step edges that serve as active dissolution sites. The possible catalytic mechanism is through the adsorption of CA on the calcite surface, followed by proton transfer from the CA catalytic center to the calcite surface during CO2 hydration. This study shows that the accessibility of CA to particulate inorganic carbon (PIC) in the ocean is critical in properly estimating oceanic CaCO3 and alkalinity cycles. © 2020 American Geophysical Union. Issue Online: 29 September 2020; Version of Record online: 29 September 2020; Accepted manuscript online: 21 September 2020; Manuscript accepted: 14 September 2020; Manuscript revised: 08 September 2020; Manuscript received: 11 June 2020. This work was supported by the National Science Foundation (NSF) Ocean Acidification grants (OCE1220600, OCE1220302 and OCE 1559004) and the University of Southern California (USC) Dornsife Doctoral Fellowship. We thank Adam V. Subhas for his helpful discussions in preparing the experiments and the manuscript. Data Availability Statement: Data set for this research is available in this inâ€text data citation reference: Dong, S., Berelson, W., Teng, H., Rollins, N., Pirbadian, S., Elâ€Naggar, M., Adkins, J. (2020). Step velocities during calcite dissolution in seawater with and without carbonic anhydrase, version 1.0. Interdisciplinary Earth Data Alliance (IEDA). https://doi.org/10.26022/IEDA/111627. Accessed 2020â€09â€08. Published - 2020GL089244.pdf Supplemental Material - ...