Carbonic Anhydrase From Nicotiana Tabacum Leaves

Authors: Nazan DEMİR, Yaşar DEMİR

Abstract: In this study, carbonic anhydrase (CA: carbonate hydrolyase; E.C.4.2.1.1) was purified from adult {\it Nicotiana tabacum} leaves and studied biochemically. The enzyme was purified twice times by using (NH$_4)_2SO_4 precipation and DEAE-cellulose column chromatography, and its activity was determined for two different substrates (CO_2 and p-nitrophenyl acetate). The enzyme obtained from the ion exchange column was purified 40.7 fold and the purity was controlled by 3\%-10\% discontinuous SDS-PAGE. The pH of the purified enzyme varied between 6.0 and 7.2, the optimum being 6.9. V_{max} and K_m values were calculated with p-nitrophenyl acetate (0.1524 mM, 0.5446 mM, respectively) as substrate. The optimum temperature for the enzyme was 40^{\circ}C. The molecular weight of the enzyme and of the subunits were found to be approximately \approx137.000 daltons and \approx 22.800 daltons, respectively. The results indicate that 6 subunits are present. Changes in enzyme activity were determined in the presence of caffeine, nicotine, metal ions and some chemicals.

Keywords: Carbonic anhydrase, {\it Nicotiana tabacum,} caffeine, nicotine

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