EXPRESSION OF GLUTARYL7-AMINOCEPHALOSPORANIC ACID ACYLASE IN ESCHERICHIA COLI BL21(DE3) AND IMMOBILIZATION OF RECOMBINANT ENZYME ON NANOPOROUS MATERIALS
Keywords:7-ACA, Cephalosporins, E. coliBL21(DE3)/[pET22b( ), , gla], enzyme immobilization, GLA, SBA-15.
The synthesis of 7-ACA from cephalosporin C (CPC) by a two-step bioconversion using D-amino acid oxidase (DAAO) and glutaryl 7-ACA acylase (GLA) has been effectively and largely applied in pharmaceutical industry. In this study, the gene gla coding for 720-amino acid GLA from plasmid pUC57::gla was analyzed and successfully inserted into vector pET22b(+) to form expression vector pET22b(+)::gla. The newly constructed expression vector pET22b(+)::gla was cloned and then transformed into Escherichia coli BL21(DE3) to generate recombinant strain E. coli BL21(DE3)[pET22b(+)::gla]. The suitable conditions for expression of gla gene were in LB medium at 30 oC and induced by 0.4 mM of Isopropyl β-D-1-thiogalactopyranoside (IPTG) for 3 hours. Under the chosen culturing parameters, expression of gla gene by E. coli BL21(DE3)/[pET22b(+)::gla] resulted in a recombinant GLA (rGLA) with molecular weight of 83 kDa and catalytic activity of 2.7 U/mg of total protein. Experimental research on immobilization of rGLA onto ten nanoporous materials were showed that, SBA-15 was the best one for immobilization of rGLA, reaching activity of immobilized enzyme of 22.2 U/g matrix. Furthermore, optimal conditions of procedure for immobilizing rGLA on nanomaterials (SBA-15) were determined as follows: temperature is 25 °C, pH7.0 and immobilization time –60 minutes. Therefore the results reported in this study revealed the successfully heterologous expression of GLA in recombinant E. coli and potential immobilization of enzyme on inorganic nano-materials.
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