GlsA1 (glutaminase1) belongs to the large superfamily of serine-dependent beta-lactamases and penicillin-binding proteins. They are present in most bacteria and eukaryotes and catalyze the hydrolytic deamidation of l-glutamine to l-glutamate and free NH4+. Recombinant E.coli glsA1 protein, fused to His-tag at Nterminus, was expressed in E.coli and purified by using conventional chromatography techniques.