title: Heterogeneous origin of carbonic anhydrase activity of thylakoid membranes.
abstract: Carbonic anhydrase activities of pea thylakoids as well as thylakoid fragments enriched either in Photosystem 1 (PS1-membranes) or Photosystem 2 (PS2-membranes) were studied. The activity of PS1-membranes if calculated on chlorophyll basis was much higher than the activity of PS2-membranes. Acetazolamide, a non-permeable inhibitor of carbonic anhydrases, increased carbonic anhydrase activity of PS2-membranes at concentrations lower than 10(-6) M and suppressed this activity only at higher concentrations. A lipophilic inhibitor of carbonic anhydrases, ethoxyzolamide, effectively suppressed the carbonic anhydrase activity of PS2-membranes (I50 = 10(-9) M). Carbonic anhydrase activity of PS1-membranes was suppressed alike by both inhibitors (I50 = 10(-6) M). In the course of the electrophoresis of PS2-membranes treated with n-dodecyl-beta-maltoside "high-molecular-mass" carbonic anhydrase activity was revealed in the region corresponding to core-complex of this photosystem. Besides, carbonic anhydrase activity in the region of low-molecular-mass proteins was discovered in the course of such an electrophoresis of both PS2- and PS1-membranes. These low-molecular-mass carbonic anhydrases eluted from corresponding gels differed in sensitivity to specific carbonic anhydrase inhibitors just the same as PS1-membranes versus PS2-membranes. The results are considered as evidence for the presence in the thylakoid membranes of three carriers of carbonic anhydrase activity.
authors.affiliation: Institute of Basic Biological Problems, Russian Academy of Sciences, 142290 Pushchino, Russia.
authors.forename: L K
authors.initials: LK
authors.lastname: Ignatova
authors.forename: N N
authors.initials: NN
authors.lastname: Rudenko
authors.forename: M S
authors.initials: MS
authors.lastname: Khristin
authors.forename: B N
authors.initials: BN
authors.lastname: Ivanov
mesh_terms: D000086:Acetazolamide / Q000494:pharmacology; D002257:Carbonic Anhydrase Inhibitors / Q000494:pharmacology; D002256:Carbonic Anhydrases / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D005016:Ethoxzolamide / Q000494:pharmacology; D005960:Glucosides / Q000494:pharmacology; D018532:Pisum sativum / Q000201:enzymology / Q000378:metabolism; D045331:Photosystem I Protein Complex / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism; D020524:Thylakoids / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism
chemical_list: D002257:Carbonic Anhydrase Inhibitors; D005960:Glucosides; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; C040358:dodecyl maltoside; D002256:Carbonic Anhydrases; D000086:Acetazolamide; D005016:Ethoxzolamide