Screening for Type II L-Asparaginases: Lessons from the Genus Halomonas

Document Type : Research article


1 Department of Pharmaceutical Biotechnology, School of Pharmacy, Shahid Beheshti University of Medical Sciences, Tehran, Iran

2 Department of Drug and Food Control, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran


Among the two types of bacterial L-asparaginases, only type II enzymes have been used in
the treatment of acute lymphoblastic leukemia owing to their higher affinity for L-asparagine.
However, current screening media used for the isolation of L-asparaginase-producing
microorganisms do not discriminate between the two types of L-asparaginase. During an
optimization study conducted to increase L-asparaginase production by environmental
Halomonas isolates, it was noticed that the pattern of L-asparaginase production in response
to variations in glucose concentration varied between different isolates suggesting that they
differ in their ability to produce type II L-asparaginases, an observation that was confirmed by
further experiments. Bioinformatics analysis of available Halomonas whole genome sequences
revealed that indeed some species of this genus possess both L-asparaginase types while others
possess only type I enzymes. By comparing the growth pattern of these isolates on different
media, we propose that by omitting glucose, reducing the concentration of L-asparagine and
providing an alternative nitrogen source in L-asparaginase screening media it may be possible
to differentiate between type I and type II activities.


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