RESUMO
Comparative analysis of the transport activity of proton pumps (plasmalemma H+-ATPase, vacuolar H+-ATPase, and vacuolar H+-pyrophosphatase) in the membrane preparations obtained from coleoptile cells ofetiolated maize seedlings (Zea mays L.) was carried out. The highest level ofvacuolar pyrophosphatase activity was observed during the early development of coleoptile cells under growth intensification through the elongation. The role of ATPase pumps of tonoplast and plasmalemma in the transport of hydrogen ions increases during further development. The plasmalemma activity in this process is higher. When the growth stops, the activity of proton pumps becomes significantly lower. Nevertheless, their substrate specificity and sensitivity to proton pump inhibitors do not change, which can be an evidence of physiological significance of pumps in the maintenance of cell homeostasis.
Assuntos
Cotilédone/enzimologia , Pirofosfatase Inorgânica/metabolismo , ATPases Translocadoras de Prótons/metabolismo , Plântula/enzimologia , ATPases Vacuolares Próton-Translocadoras/metabolismo , Zea mays/enzimologia , Laranja de Acridina , Trifosfato de Adenosina/metabolismo , Trifosfato de Adenosina/farmacologia , Transporte Biológico Ativo/fisiologia , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Cotilédone/efeitos dos fármacos , Cotilédone/crescimento & desenvolvimento , Dextranos , Fluoresceína-5-Isotiocianato/análogos & derivados , Corantes Fluorescentes , Homeostase/fisiologia , Pirofosfatase Inorgânica/antagonistas & inibidores , Inibidores da Bomba de Prótons/farmacologia , ATPases Translocadoras de Prótons/antagonistas & inibidores , Plântula/efeitos dos fármacos , Plântula/crescimento & desenvolvimento , Especificidade por Substrato , ATPases Vacuolares Próton-Translocadoras/antagonistas & inibidores , Vacúolos/efeitos dos fármacos , Vacúolos/enzimologia , Valinomicina/farmacologia , Zea mays/efeitos dos fármacos , Zea mays/crescimento & desenvolvimentoRESUMO
The activity of plasma membrane H+-ATPase was cytochemically investigated in parenchyma cells of maize coleoptile. The intensity of ATP hydrolysis was determined by deposition of electron density sediment formed by lead and inorganic phosphate. The shift in the enzyme distribution and its hydrolytic activity in the plasma membrane of maize coleoptile cells were revealed within seedling development. The intensity of precipitation was quantified by Image Pro Plus. The maximum precipitation was determined in plasma membrane of coleoptile cells of 4-days-old seedlings. The data obtained coincide with the results of previous biochemical investigation of H+-ATPase hydrolytic activity, provided with purified plasma membrane vesicles. Nevertheless the increase in quantity and(or) activity of the enzyme was observed at the 4th day of seedling development which was characterized by slowing down of growth intensity. The results show the possibility of changes in quantity and distribution of the enzyme in plasma membrane during the differentiation process of cell elongation.