Normal lymphocytes can synthesize l-asparagine from aspartate using the enzyme asparagine synthetase, which is not expressed in tumour cells (Broome 1961).
L-Asparaginase ( l-ASNase l-asparagine amidohydrolase EC 3.5.1.1) is used in the treatment of acute lymphocytic leukaemia (ALL) by catalysing the hydrolysis of asparagine, an essential growth factor for leukaemic cells. This study demonstrates the diversity of filamentous fungi isolated from the Brazilian Caatinga Biome and the importance of knowledge of the microbial metabolism to obtain high concentrations of biotechnological products. In order to minimize the side effects caused by bacterial l-ASNase, the search of eukaryotic micro-organism for l-ASNase was carried out in fungi. The work reported here represents the first attempt to produce l-ASNase by filamentous fungi isolated from Brazil and offers a promising alternative eukaryotic source for l-ASNase production. Fermentation conditions were then optimized in a 5-l bioreactor system to produce a maximum volumetric yield of 108 U total of l-ASNase activity. When Aspergillus terreus strain S-18 was cultured in a proline-enriched medium, intracellular l-ASNase was expressed in concurrence with reduced l-glutaminase ( l-GLUase) and protease activities. Thirty-two filamentous fungi were investigated in this study.
This report describes screening for l-ASNase production by filamentous fungi isolated from the Brazilian Caatinga, and the optimization of fermentation parameters to increase fungal growth and improve yield in the production of l-ASNase. The aim of this study was to find new eukaryotic sources of the l-asparaginase ( l-ASNase), since the prokaryotic sources of the enzyme are well-reported as causing allergic hypersensitivity reactions in a significant number of patients.
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