Optimization and characterization of antileukemic l-asparaginase produced by Fusarium solani endophyte

Abstract

l-asparaginase is an antileukemic enzyme that hydrolyzes l-asparagine into l-aspartic acid and ammonia, causing cell starvation and apoptosis in susceptible leukemic cell populations. Currently, l-asparaginase obtained from bacterial sources is constrained by several issues, including lesser productivity, stability, selectivity, and higher toxicity. The goal of this study is to provide fungal l-asparaginase with in-vitro effectiveness towards different human carcinomas. l-asparaginase from endophytic Fusarium solani (Gene Bank accession number MW209717) isolated from the roots of the medicinal plant Hedera helix L. was characterized and optimized experimentally for maximum l-asparaginase production in addition to evaluating its subsequent cytotoxicity towards acute monocytic leukemia and human skin fibroblast cell lines. The enzyme production was maximized using potato dextrose media (15.44 IU/ml/hr) at the 5th and 6th days of fermentation with incubation temperature 30 °C, 3% asparagine, 150–180 rpm agitation rate and a 250 ml flask. Enzyme characterization studies revealed that the enzyme maintained its thermal stability with temperatures up to 60 °C. However, its optimal activity was achieved at 35 °C. On measuring the enzymatic activity at various temperatures and different pH, maximum enzyme activity was recorded at 40 °C and pH 8 using 0.1 M asparagine concentration. Results also revealed promising cytotoxic activity against acute monocytic leukemia with IC50 = 3.66 µg/ml and low cytotoxicity against tested normal human skin fibroblast cell line which suggested that it might have selective toxicity, and consequently it could be used as a less toxic alternative to the current formulations.