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Influence of the alternative respiratory pathway on the adenylate pools in heterotrophic Euglena gracilis
Author(s) -
Benichou Pierre,
Bomsel JeanLoup,
Vinel Dominique,
Claisse Maurice L.,
Calvayrac Régis
Publication year - 1990
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1990.tb06746.x
Subject(s) - euglena gracilis , euglena , energy charge , antimycin a , adenylate kinase , biology , salicylhydroxamic acid , biochemistry , rotenone , oligomycin , cytochrome , electron transport chain , mitochondrion , enzyme , chloroplast , atpase , gene
Etiolated Euglena gracilis Pringsheim, strain Z, were cultured in a lactate medium either in the presence of 2 μ M antimycin A for cells adapted to this inhibitor, or in the absence of antimycin A for controls. The adenylates (ATP, ADP and AMP) and the energy charge (EC) were followed during the growth of both types of cells. The effects of KCN, salicylhydroxamic acid (SHAM) and rotenone on the respiration and the adenylate pool, were investigated during the exponental and stationary phases. EC values of controls and antimycin‐adapted cells were not significantly different during culture. In the logarithmic phase, EC of controls was unaffected by 3 m M SHAM, an inhibitor of the alternative pathway, but markedly decreased by 0.3 m M KCN, which inhibits the cytochrome pathway. In contrast, in antimycin‐adapted Euglena , in which the cytochrome pathway was blocked, ATP content and EC were markedly lowered in the presence of SHAM but slightly increased by 0.3 m M KCN. The combination of the preceeding treatments, as well as 15 m M KCN alone, were deleterious for both types of cells, in the logarithmic and the late stationary phases. The data indicate that the energy level in Euglena was dependent on the alternative pathway when the cytochrome pathway was blocked. Such dependence could be explained by the engagement of the first rotenone‐sensitive site of phosphorylation. Indeed, 50 μ M rotenone caused a similar relative decrease of oxygen consumption and ATP content in controls and in antimycin‐adapted Euglena . In the absence of cytochrome respiration, the alternative pathway allowed electrons to flow through this first segment of the respiratory chain, and ATP production by the first site of phosphorylation.