[Inhibitor of aminoglycoside phosphotransferases from Micromonospora sp.--a producer of sisomicin].

A substance inhibiting the activity of aminoglycoside-3-'-phosphotransferases of both the actinomycetous and the bacterial origin was detected in the filtrates of the culture fluid and mycelium of Micromonospora sp. producing sisomicin. The activity of the substance against the aminoglycoside inactivating enzymes of different types was studied. It was shown that the quantity of the inhibitor in the culture fluid of Micromonospora sp. correlated with intensity of sisomocin production. Under conditions not providing production of the antibiotic the inhibitory activity was lacking. The inhibitor was purified by ion exchange chromatography on Amberlite CG-50 and KM-cellulose (NH+4 form), gel filtration through Sefadex G-50 and preparative paper chromatography. Stability of the inhibitor at different pH values and different temperatures, its sensitivity to certain enzymes and behaviour in high voltage electrophoresis were studied. The results of ultrafiltration showed that the molecular weight of the inhibitor was relatively low: less than 1000 D.