l-asparaginase production and enhancement by Sarocladium strictum: In vitro evaluation of anti-cancerous properties

Utilization of l-asparaginase has been one of the effective strategies for the treatment of lymphoblastic leukaemia. Since the currently used bacterial l-asparaginase causes side effects, searching for new enzyme sources has been an active field of research. This study focuses on the characterization of an l-asparaginase-producing fungal strain.

Sarocladium strictum was identified as a potent enzyme-producing strain. For the enhancement of enzyme production, we used two-level factorial design and response surface methodology. The optimization of significant factors showed a 1·84-fold increase in enzyme production. The K_m and V_max values of the enzyme were 9·74 mmol l^-1 and 8·19 μmol min^-1 . The toxicity of the produced l-asparaginase was measured on K562 and HL60 cancer cell lines and L6 as normal cells. The IC₅₀ values were calculated as 0·4 and 0·5 IU ml^-1 for K562 and HL60 respectively and no significant effect was observed in L6. BrdU proliferation and caspase-3 activity assay in l-asparaginase treated HL60 and K562 cells indicated that cell proliferation rates and apoptotic cell death were reduced.

The cytotoxic properties of the produced fungal enzyme indicated significant growth inhibition in cancer cells while having a little toxic effect on normal cells. The possibility of mass production alongside having suitable cytotoxic and kinetic properties suggest the probable use of the produced l-asparaginase for further researches as a potential chemotherapeutic agent.

The lack of significant l-glutaminase activity and promising toxicity properties in S. strictum and the closer evolutionary relativeness of fungi enzymes to human enzymes compared to bacterial enzymes suggest a new source with lower toxicity and anti-cancerous properties, causing less side effect problems.