Silicases

The silicases are a family of enzymes that catalyze rearrangement of silicon-oxygen bonds and are found in some sea sponges.^[1] ^[2]

The by-product of this reaction is silicic acid. ^[3]

A zinc atom is held in place by three histidine residues. A fourth position on the zinc extracts a hydroxy group from water.

This reacts with an amorphous fragment of hydrated silica to break off silicic acid and leave zinc attached to the larger silica frament.

Zn-O-H + Si-O-Si(OH)₃ → Zn-O-Si + H-O-Si(OH)₃

This is then hydrolysed: ^[1]

Zn-O-Si + H₂O → Zn-OH + HO-Si

Silicases are related to a more common enzyme in animals, carbonic anhydrase. In the human body the carbonic anhydrase most similar to the sponge silicase is type II (CA-II).^[1] ^[4]

References

^ ^a ^b ^c Schröder, Heinz C.; Krasko, Anatoli; Le Pennec, Gaël; Adell, Teresa; Wiens, Matthias; Hassanein, Hamdy; Müller, Isabel M.; Müller, Werner E. G. (2003). "Silicase, an Enzyme Which Degrades Biogenous Amorphous Silica: Contribution to the Metabolism of Silica Deposition in the Demosponge Suberites domuncula". In Müller, Werner E. G. (ed.). Silicon Biomineralization: Biology — Biochemistry — Molecular Biology — Biotechnology. Progress in Molecular and Subcellular Biology. Vol. 33. Springer-Verlag Berlin Heidelberg. pp. 249–268. doi:10.1007/978-3-642-55486-5_10. Retrieved 12 January 2026.
^ Enhrlich, Hermann; Demadis, Konstantinos D.; Pokrovsky, Oleg; Koutsoukos, Petros G. (2010). "Modern Views on Desilicification: Biosilica and Abiotic Silica Dissolution in Natural and Artificial Environments". Chemical Reviews. 110 (8). doi:10.1021/cr900334y.
^ Kaur, Prabhjot; Sharma, Anjali; Bhardwaj, Nishi Kant; Singh, Amarjit; Dalal, Sunita; Sharma, Jitender (2022). "A novel, simple, and quick plate assay to screen silicolytic bacteria and silicase production using different substrates". Bioresource Technology Reports. 17. Elsevier. Retrieved 12 January 2026.
^ Angeli, Andrea; De Luca, Viviana; Capasso, Clemente; Di Constanzo, Luigi F; Supuran, Claudiu T (2024). "Comparative CO₂ and SiO₂ hydratase activity of an enzyme from the siliceous demosponge Suberitesdomuncula". Arch Biochem Biophys. 758. doi:10.1016/j.abb.2024.110074. Retrieved 12 January 2026.

[schr-1] Schröder, Heinz C.; Krasko, Anatoli; Le Pennec, Gaël; Adell, Teresa; Wiens, Matthias; Hassanein, Hamdy; Müller, Isabel M.; Müller, Werner E. G. (2003). "Silicase, an Enzyme Which Degrades Biogenous Amorphous Silica: Contribution to the Metabolism of Silica Deposition in the Demosponge Suberites domuncula". In Müller, Werner E. G. (ed.). Silicon Biomineralization: Biology — Biochemistry — Molecular Biology — Biotechnology. Progress in Molecular and Subcellular Biology. Vol. 33. Springer-Verlag Berlin Heidelberg. pp. 249–268. doi:10.1007/978-3-642-55486-5_10. Retrieved 12 January 2026.

[2] Enhrlich, Hermann; Demadis, Konstantinos D.; Pokrovsky, Oleg; Koutsoukos, Petros G. (2010). "Modern Views on Desilicification: Biosilica and Abiotic Silica Dissolution in Natural and Artificial Environments". Chemical Reviews. 110 (8). doi:10.1021/cr900334y.

[3] Kaur, Prabhjot; Sharma, Anjali; Bhardwaj, Nishi Kant; Singh, Amarjit; Dalal, Sunita; Sharma, Jitender (2022). "A novel, simple, and quick plate assay to screen silicolytic bacteria and silicase production using different substrates". Bioresource Technology Reports. 17. Elsevier. Retrieved 12 January 2026.

[4] Angeli, Andrea; De Luca, Viviana; Capasso, Clemente; Di Constanzo, Luigi F; Supuran, Claudiu T (2024). "Comparative CO₂ and SiO₂ hydratase activity of an enzyme from the siliceous demosponge Suberitesdomuncula". Arch Biochem Biophys. 758. doi:10.1016/j.abb.2024.110074. Retrieved 12 January 2026.

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