Carbonic anhydrase and zinc in plant physiology.

Dalila Jacqueline Escudero-Almanza1,Damaris Leopoldina Ojeda-Barrios1*, Ofelia Adriana Hernández-Rodríguez1, Esteban Sánchez-Chávez2, Teresita Ruiz-Anchondo1, Juan Pedro Sida-Arriola1

Carbonic anhydrase (CA) (EC: catalyzes the rapid conversion of carbon dioxide plus water into a proton and the bicarbonate ion (HCO3-) that can be found in prokaryotes and higher organisms; it is represented by four different families. Carbonic anhydrase is a metalloenzyme that requires Zn as a cofactor and is involved in diverse biological processes including pH regulation, CO2 transfer, ionic exchange, respiration, CO2 photosynthetic fixation, and stomatal closure. Therefore, the review includes relevant aspects about CA morphology, oligomerization, and structural differences in the active site. On the other hand, we consider the general characteristics of Zn, its geometry, reactions, and physiology. We then consider the CA catalysis mechanism that is carried out by the metal ion and where Zn acts as a cofactor. Zinc deficiency can inhibit growth and protein synthesis, and there is evidence that it reduces the CA content in some plants, which is a relationship addressed in this review. In leaves, CA represents 20.1% of total soluble protein, while it is the second most abundant in the chloroplast after ribulose 1,5-disphosphate carboxylase/oxygenase (RuBisCO). This facilitates the supply of CO2 to the phosphoenolpyruvate carboxylase in C4 and CAM plants and RuBisCO in C3 plants.

Keywords: Cofactor, metal ion catalysis, metalloenzyme, zinc deficiency, CO2 transfer.
1Universidad Autónoma de Chihuahua, Facultad de Ciencias Agrotecnológicas, Escorza 900. Col. Centro. 31000. Apartado Postal 24 Chihuahua, Chihuahua, México. *Corresponding author (dojeda@uach.mx).
2Centro de Investigación en Alimentación y Desarrollo, A.C. Av. 4ta Sur 3820, Fracc. Vencedores del Desierto. 33089. Cd. Delicias, Chihuahua, México.