Metabolism of Trehalose in Euglena gracilis

Abstract

Abstract Trehalose phosphorylase, an enzyme found in cell-free extracts of Euglena gracilis var. bacillaris, was purified 75-fold by treatment with protamine sulfate, centrifugation at 200,000 x g, and chromatography in a column of hydroxylapatite. This enzyme catalyzes the reversible phosphorolytic splitting of trehalose, yielding β-glucose 1-phosphate and glucose as products. The optimum pH of the reaction was 7.0 for phosphorolysis and 6.3 for the synthesis of trehalose. The equilibrium constant changes with pH. It was 4.2 at pH 7.0 and 17 at pH 6.3. The enzyme is very unstable in the absence of inorganic phosphate, α- or β-glucose 1-phosphate. Measurements in sucrose gradient gave a molecular weight of about 344,000. This enzyme together with a phosphoglucomutase for β-glucose 1-phosphate found in the same Euglena extracts would constitute a new catabolic pathway for trehalose.