Aspergillus flavipes methionine γ-lyase-dextran conjugates with enhanced structural, proteolytic stability and anticancer efficiency

Abstract

Aspergillus flavipesl-methionine γ-lyase (AfMGL) has been recognized as a powerful broad range anticancer agent. However, catalytic instability and antigenicity are the main challenges of its applications in vivo. Thus, the objective of this study was to investigate the influence of conjugation with dextran on AfMGL biochemical properties and functionality. The activity of dextran AfMGL conjugates was 50% of the free MGL that consistent with the extent of occupied surface reactive amino groups. The accessibility of reactive ε-amino groups on dextran AfMGL surface was reduced by 70% normalizing to free enzyme. The thermal stability of dextran AfMGL was increased by two folds over the free enzyme. The dextran AfMGL had a higher resistance to proteinase K, retaining about 70% of its initial activity comparing to 20% to the native enzyme after 30min of proteolysis at 37°C. The in vivo half-life time of dextran modified AfMGL in New Zealand rabbits was increased by 2.3 folds comparing to free enzyme. The in vitro anticancer activity of the free and modified AfMGL was evaluated against five tumor cell lines (MCF-7, HEPG-2, HCT, PC3, HEP-2). The activity of AfMGL towards the tested tumor cells was significantly increased upon dextran conjugation suggesting the dramatic increasing of MGL hydrophilicity and catalytic efficiency. Dextran solution was used as negative control.