Characterization of L-Asparaginase Free of L-Glutaminase and Urease Activity Produced by the Marine Paraconiothyrium cyclothyrioides Strain MABIK FU00000820

Asparaginase (ASNase) is an important enzyme used to treat acute lymphoblastic leukemia. However, the clinical use of the currently available ASNases is limited because of their associated side effects. One of the major reasons for these adverse effects is the coactivity of glutaminase (GLNase) with ASNase. Furthermore, the concomitant urease activity may exacerbate the toxicity associated with ASNase treatment. Therefore, identifying novel sources of ASNase with minimal or no glutaminase and urease activities is important. We isolated a marine fungal strain, MABIK FU00000820, which produced ASNase free of GLNase and urease activity. Based on morphological and phylogenetic analyses, this strain was identified as Paraconiothyrium cyclothyrioides. The crude extract of intracellular ASNase exhibited the maximum activity at 37–50 °C, pH 8.5, and 0% (w/v) NaCl. In addition, the enzyme stability assay showed that the P. cyclothyrioides ASNase pre-treated at 4–25 °C for 2 h retained 77% of its activity compared to the untreated control. Based on the available literature, this appears to be the first study to investigate ASNase from P. cyclothyrioides, and it is of particular significance because the enzyme exhibits neither GLNase nor urease activity.