Reversible pH-dependent activation/inactivation of CF(1)-ATPase of spinach chloroplasts

Abstract

The aim of the work was to study the reverse pH-dependent regulation of the enzymatic activity of the catalytic part of ATP synthase (EC 3.6.3.14) of chloroplast – coupling factor CF1. It was shown that the short-term incubation of isolated CF1 in the media with pH 4.5 or 3.5 leads to inactivation of Ca2+-ATPase, which is rapidly (t1/2 ~ 1 min) restored in the medium containing 0.5-10 mM bicarbonate at pH 7.8. After acid treatment, the rate of Mg2+-ATPase reaction was also stimulated in the presence of 1 mM bicarbonate (рН 7.8; 37 °С). The increase in Ca2+– and Mg2+-АТР activity of CF1 associated with the addition of NaHCO3 solution was completely eliminated after the introduction of 50 mM acetazolamide – a specific inhibitor of carbonic anhydrase. The obtained results suggest the existence of the bound bicarbonate in the CF1 structure, which apparently participates in proton transfer.

Keywords

• acetazolamide
• activation/inactivation
• ATP hydrolysis
• CF1-ATPase
• pH-dependence