Effect of Ammonium Ion on A Rapid Breakdown of Paramylon (β-1, 3-glucan) in Protist Euglena gracilis

摘要

Ammonium ion induced a rapid breakdown of paramylon in carbon-starved cells of the bleached mutant Euglena gracilis SM-ZK. Cells showing a rapid breakdown of paramylon contained the induced high activities of the paramylon degrading enzymes; β-1, 3-phosphorylase (EC 2.4.1.97) and laminarinase (EC 3.2.1.16). The ammonium ion induced breakdown of paramylon appeared to be associated with the increase of amino acid pools in the cells. Co-existence of ammonium ion and cycloheximide, an inhibitor of cytoplasmic protein synthesis, greatly delayed the breakdown of paramylon. We suggest that the main role of paramylon in E. gracilis is to provide the necessary energy for surviving periods in the absence of suitable food sources and to provide the carbon necessary for amino acids in cytoplasmic metabolisms.