Multiple sources of carbonic anhydrase activity in pea thylakoids: soluble and membrane-bound forms

Abstract

Carbonic anhydrase (CA) activity of pea thylakoids, thylakoid membranes enriched with photosystem I (PSI-membranes), or photosystem II (PSII-membranes) as well as both supernatant and pellet after precipitation of thylakoids treated with detergent Triton X-100 were studied. CA activity of thylakoids in the presence of varying concentrations of Triton X-100 had two maxima, at Triton/chlorophyll (triton/Chl) ratios of 0.3 and 1.0. CA activities of PSI-membranes and PSII-membranes had only one maximum each, at Triton/Chl ratio 0.3 or 1.0, respectively. Two CAs with characteristics of the membrane-bound proteins and one CA with characteristics of the soluble proteins were found in the medium after thylakoids were incubated with Triton. One of the first two CAs had mobility in PAAG after native electrophoresis the same as that of CA residing in PSI-membranes, and the other CA had mobility the same as the mobility of CA residing in PSII-membranes, but the latter was different from CA situated in PSII core-complex (Ignatova et al. 2006 Biochemistry (Moscow) 71:525-532). The properties of the "soluble" CA removed from thylakoids were different from the properties of the known soluble CAs of plant cell: apparent molecular mass was about 262 kD and it was three orders more sensitive to the specific CA inhibitor, ethoxyzolamide, than soluble stromal CA. The data are discussed as indicating the presence of, at least, four CAs in pea thylakoids.

Carbonic anhydrase activity in Arabidopsis thaliana thylakoid membrane and fragments enriched with PSI or PSII

“…The nature of the low molecular mass carrier of CA activity was not ascertained till now. The data obtained in this study and in others as well Rudenko et al 2007) imply that this carrier is an individual protein, which possesses unique characteristics of its CA activity, namely it can be stimulated by AA and azide at low concentrations. Besides, this CA is very sensitive to EZ.…”

Photoassembly of the water-oxidizing complex in photosystem II

“…However the latter results are at contradiction with earlier work showing that neither Mn 2+ nor Ca 2+ have specific binding sites on the spinach 33-MSP when studied as a free protein [71]. Given the low activity and requirement for Mn 2+ there appears to be no clear physiological significance for this site of bicarbonate activity in PSII in vivo [65,72].…”

“…This conversion uses enzymes known as carbonic anhydrase which exist in multiple subclasses, including a thylakoid membrane associated carbonic anhydrase [65]. Some alkalophilic cyanobacteria (Arthrospira genus) that originate from volcanic soda lakes prefer very high extracellular carbonate concentrations reaching 0.4 to 1.2 M NaCO 3 .…”

Drought and Salinity Stress: Changes in Hydratase and Dehydratase Activities of Thylakoid-Associated Carbonic Anhydrase in Pea Seedlings

“…4), that is, less downregulation. Rudenko et al (2007) andIvanov et al (2007) proposed a scheme with emphasis on the operation of tCA that uses lumenal protons to dehydrate HCO À 3 . These protons are delivered to the active center of tCA along a channel in the thylakoid membrane.…”

“…The possible role of thylakoid-associated carbonic anhydrase (tCA) in this mechanism of PSII downregulation has recently been suggested (Lazova et al 2009). The tCA has several forms and locations (Rudenko et al 2007) and possesses a variety of functions of great importance for influencing photosynthetic processes. The association between tCA activity and photosynthetic electron transport in thylakoid membranes has been discussed previously (Vaklinova et al 1982;Stemler 1986;Shin et al 1989;Moskvin et al 1995).…”