High-yield production and functional analysis of novel rhizobial-type glutaminase-free L-asparaginase from Paenibacillus thiaminolyticus.

L-Asparaginases are enzymes known for decades due to their use in medicine for the treatment of acute lymphoblastic leukemia. Recently, they have also found application in the food industry, and other possibilities are emerging in the treatment of infectious diseases or in the design of biosensors. For this reason, an ongoing effort has been made to find and characterize new enzymes with properties suitable for these specific applications. In this work, L-asparaginase from Paenibacillus thiaminolyticus (isoenzyme 1) belonging to the least explored group of L-asparaginases derived from L-asparaginase from Rhizobium etli was recombinantly produced with high yields (335 mg per L of culture medium) in E. coli cells and characterized: K_M = (26 ± 8) mmol L^-1, pH_opt = 10.3, without L-glutaminase and urease activity. A probable oligomeric structure (homodimer) was derived by computer modeling and confirmed by gel chromatography experiments. The results of this work extend the current limited knowledge about the poorly described class of R. etli L-asparaginases. Moreover, this L-asparaginase exhibits suitable properties for use in biosensor construction because of the high yields during recombinant production, K_M value, stability, and absence of L-glutaminase activity.