Double-osmotic-shock procedure to prepare gentamicin adenine mononucleotide transferase for the enzymatic assay of gentamicin

The release of gentamicin adenine mononucleotide transferase during single, cold, osmotic-shock treatment of Escherichia coli K-12 W677/HJR66 is not always maximal. The quantity of gentamicin adenine mononucleotide transferase in osmotic extracts could be significantly increased when a double-shock procedure was performed.