Degradation of the compatible solute trehalose in Ectothiorhodospira halochloris: isolation and characterization of trehalase

Trehalase, which hydrolyzes the disaccharide trehalose to -d-glucose was isolated and partially purified (124-fold) from the phototrophic halo-alkaliphilic bacterium Ectothiorhodospira halochloris. The molecular mass was determined to be 480,000 and the isoelectric point pH 5.6. Temperature optimum was found to be 40°C and the pH-optimum 7.8–8.1. In spite of its high K_m-value of 0.5 M, trehalase of E. halochloris was shown to be specific for trehalose. Trehalase is activated by phosphate which is, however, not involved in the reaction mechanism. The enzyme is activated by the compatible solute betaine and inhibited by salts. In the presence of betaine the K_m-value is lowered from 0.5 M to 0.16 M; moreover, betaine partially protects enzymatic activity from salt inhibition. The findings indicate that betaine might regulate the trehalose level in the cells by affecting trehalase activity.