Characterization and application of an L-asparaginase derived from the metagenome of fecal microbiota

Abstract:

l-asparaginase, a key enzyme in amino acid metabolism, is widely used in the food and pharmaceutical industries. The gut microbiota and its product l-asparaginase are closely associated with host health and diseases. [Objective] This study aims to acquire a novel l-asparaginase gene from gut microbiota and explore its enzymatic characteristics and potential applications. [Methods] An l-asparaginase gene was cloned from the metagenome of the fecal microbiota of Nomascus concolor and heterologously expressed in Escherichia coli BL21(DE3). The enzymatic properties of the expressed protein were determined. Furthermore, the potential applications of this protein were explored, including processing potato chips and treating cancer cells. [Results] The cloned l-asparaginase gene, NCasn5, was 996 bp. It encoded the recombinant enzyme NCasn5 with a molecular weight of 37.296 kDa, optimal activity at pH 8.0 and 60 °C, K_m of (3.33±0.21) mmol/L, V_max of (836.30±13.91) µmol/(min·mg), and a serum half-life of about 69 h in vitro at 37 °C. NCasn5 reduced the acrylamide content in potato chips by 69.35% and inhibited the growth of human liver cancer cells (QGY-7703) and human melanoma cells (A-375). [Conclusion] We obtained a novel l-asparaginase demonstrating good thermal stability and a prolonged serum half-life. This enzyme lacks the glutaminase activity and reduces acrylamide levels in potato chips. Moreover, it can induce apoptosis in the cancer cell lines QGY-7703 and A-375. These findings suggest the potential applicability of l-asparaginase in both food processing and pharmaceutical industries.