Gentamicin:adenine mononucleotide transferase: partial purification, characterization, and use in the clinical quantitation of gentamicin.

Abstract

Gentamicin: adenine mononucleotide transferase (GAT) was partially purified from R+Escherichia coli W677/HJR66. Gentamicin, kanamycin, and tobramycin and their isomers served as substrates, while gentamicin C2 had the lowest Km and the highest Vmax. Adenosine-5′-triphosphate (ATP) is the preferred nucleotide substrate with a Km of 61 μM; however, 2′-deoxy ATP, guanosine-5′-triphosphate, uridine-5′-triphosphate, and cytidine-5′-triphosphate can also be used, Data were obtained that suggested the products of the reaction are gentamicin adenine mononucleotide and pyrophosphate. GAT was used to measure concentrations of gentamicin in serum, urine, and bile. In these fluids, quantitation of added gentamicin gave values within 10% of theoretical. Correlation of the enzymatic assay of gentamicin in serum was excellent with the 18-hr microbiologic method (r = 0.952), as well as with the more rapid microbiologic technique (r = 0.934). Similar correlation coefficients were obtained when urine was examined. GAT appears to offer a rapid, specific, and sensitive means of quantitating gentamicin and certain other aminoglycoside antibiotics in body fluids.