Degradation of Paramylon by Euglena gracilis

SYNOPSIS. Protozoa of the order Euglenida contain a polysaccharide storage product, paramylon, composed of 1, 3‐linked glucose molecules arranged into an extremely resistant granule. An enzyme was purified from the soluble phase of Euglena gracilis which would degrade this polysaccharide to single glucose residues, providing the integrity of the paramylon granule was 1st disrupted by dilute base. This enzyme, a β‐1, 3 glucanase, had optimal activity at pH 5.0 and 60 C and bound tightly to base‐disrupted paramylon substrate tho not to the intact granules. The specific activity of the enzyme was doubled when cell cultures reached stationary phase, the phase where net carbohydrate utilization began. An ATP‐dependent hexokinase reaction was also present in Euglena homogenate. No phosphorylase activity has been found in Euglena. It is suggested, therefore, that Euglena do utilize their paramylon as a carbohydrate reserve and the mechanism of this utilization is by exo‐hydrolytic cleavage to free glucose followed by phosphorylation and glycolysis.