Cloning and molecular analysis of L-asparaginase II gene (ansB)

The deamination of L-asparagine to L-aspartic acid and ammonia is catalyzed by L-asparaginases (L-asparagine amino hydrolase). The enzyme L-asparaginase is widely distributed in nature from different living organisms, starting from bacteria till mammals and plants. It has been recently thought to be a therapeutic agent in treatment of various lymphoblastic leukemia diseases. There have been many attempts to isolate microorganisms that produce L-asparaginase. L-ASNase producing bacteria, Escherichia coli MG27, was previously isolated from the River Nile and identified. In this study, ansB gene, encoding L-ASNase II from E. coli MG27, was amplified by PCR, cloned and characterized by DNA sequencing. The DNA sequence was then analyzed using bioinformatics analysis and translated into amino acid sequence. Identification of highly conserved amino acid sequence motifs was conducted by comparison against the InterPro database. Analysis revealed that the protein sequence had a catalytic domain of L-asparaginase type II (IPR004550) that belong to asparaginase/glutaminase family (IPR006034) and has asparaginase/glutaminase conserved site (IPR020827). According to results predicted using PSIpred tool, ansB consists of eight α-helices and 13 β-strands.