Development of a thermally stable formulation for l-asparaginase storage in aqueous conditions

Abstract

l-Asparaginase is an enzyme broadly used in pharmaceutical and food industry. Freeze-drying of l-asparaginase is time and energy consuming, and can cause enzyme activity loss. Furthermore, temperature excursion during transport and storage may ruin its activity as well. Hence, it is necessary to develop a thermostable liquid formulation of l-asparaginase. In this study, a thermostable liquid formulation using glycine as a protecting excipient was developed based on the screening tests. The presence of glycine in the citrate⿿phosphate buffer significantly increased the melting point by 4°C and further dramatically slowed down the denaturation of l-asparaginase at 45 and 50°C. No subunit dissociation of l-asparaginase was detected by native-polyacrylamide gel electrophoresis, indicating that the denaturation of l-asparaginase was mainly caused by the changes in the secondary structure, confirmed by the circular dichroism data. This novel thermostable liquid formulation could offer significant promise for long-term storage of l-asparaginase in aqueous conditions.