EXTRACELLULAR GLUTAMINASE-FREE L-ASPARAGINASE FROM TRICHODERMA VIRIDE F2: PURIFICATION, BIOCHEMICAL CHARACTERIZATION AND EVALUATION OF ITS POTENTIAL IN MITIGATING ACRYLAMIDE FORMATION IN STARCHY FRIED FOOD

Abstract

L-asparaginase is an antitumor agent that suppresses cancer cell growth by eliminating L-asparagine from malignant cells. However, the intrinsic glutaminase activity is responsible for significant life-threatening adverse effects. Therefore, glutaminase-free L-asparaginase is far required to improve the therapeutic efficacy of L-asparaginase treatment. L-asparaginase was also used to combat the development of acrylamide in foods rich in carbohydrates cooked at high temperatures. Therefore, this study explores the purification and characterization of glutaminase-free L-asparaginase from Trichoderma viride F2 using agro-industrial residues as substrate. The enzyme was purified 36-folds with 688.1 U/mg specific activity and a final yield of 38.9% through ethanol precipitation, gel filtration on Sephadex G-100 followed by Sephadex G-200. The purified L-asparaginase is monomeric with a molecular mass of 57 kDa and exhibited optimum activity at pH 7.5 and 37 °C, which is relatively close to the human body's internal environment. The purified L-asparaginase showed high affinity and catalytic efficiency towards its natural substrate L-asparagine with K_m and V_max of 1.2 mM and 71.3 U/mL, respectively, and did not exhibit any intrinsic glutaminase activity. Among the salts tested, the univalent cations Na⁺ and K⁺ enhanced the activity by 145.7% and 163.5%, respectively, while the presence of Ag⁺ and Fe⁺³ displayed a considerable loss in activity. The enzyme showed a good anti-oxidant activity with IC₅₀ of 66.1μg/mL and was able to convert L-asparagine exist in potatoes to L-aspartic acid and ammonia, suggesting its use as anti-carcinogenic agent and as potential food industry candidate to mitigate acrylamide content in starchy fried food.