Purification of L-methionine γ-lyase (MGL) from A. fumigatus was sequentially conducted using heat treatment and gel filtration, resulting in 3.04 of purification fold and 73.9% of enzymatic recovery. The molecular mass of the purified MGL was approximately apparent at 46 KDa based on SDS-PAGE analysis. The enzymatic biochemical properties showed a maximum activity at pH 7 and exhibited plausible stability within pH range 5.0–7.5; meanwhile the highest catalytic activity of MGL was observed at 30–40 °C and the enzymatic stability was noted up to 40 °C. The enzyme molecule was significantly inhibited in the presence of Cu2+, Cd2+, Li2+, Mn2+, Hg2+, sodium azide, iodoacetate, and mercaptoethanol. Moreover, MGL displayed a maximum activity toward the following substrates, L-methionine < DL-methionine < Ethionine < Cysteine. Kinetic studies of MGL for L-methioninase showed catalytic activity at 20.608 mM and 12.34568 µM.min−1. Furthermore, MGL exhibited anticancer activity against cancerous cell lines, where IC50 were 243 ± 4.87 µg/ml (0.486 U/ml), and 726 ± 29.31 µg/ml (1.452 U/ml) against Hep-G2, and HCT116 respectively. In conclusion, A. fumigatus MGL had good catalytic properties along with significantly anticancer activity at low concentration which makes it a probably candidate to apply in the enzymotherapy field.

In the current study, thermo-tolerant fungal isolates were screened for their ability to metabolize L-methionine by L-methionine γ-lyase (MGL). Among 63 fungal isolates, fifteen isolates exhibited ability to MGL induction as evidenced by qualitative assay method using phenol red. Then, quantitative assay method indicates that fungal isolates coded as 26 & 37 were the most potent for MGL production. Fungal mycelium treatment under the sonication process proved that isolate No. 37 could be release MGL with maximum activity, meanwhile isolate No. 26 has been produced MGL extracellularly under the same culture conditions. Thereafter, characterization and identification of these two isolates was carried out by morphological, microscopic examination and molecular techniques. In consequence of this characterization, isolate No. 26 & 37 were identified as Aspergillus fumigates and Rhizomucor miehei respectively. Different culture conditions were screened by Plakket-Burmn design to define the significant parameters that affect the induction of MGL of the two fungal strains. Using the response surface method model, independent culture parameters were optimized through a central composite design (CCD) to maximize the induction of extracellular and intracellular MGL by A. fumigatus and R. miehei. Statistical optimization using Response surface methodology (RSM) revealed that yeast extract, incubation period and temperature were significant factors for MGL production by R. miehei where MGL was 8.27 U/mg. Additionally, glycerol, PH, period and inoculum size were the most efficient factors affect MGL by A. fumigatus where MGL was 12.37 U/mg.

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