家兎肝臓を用いてのペニシリンGの分解

抄録

Decomposition of penicillin G by rabbit liver was examined. By perfusion through surviving rabbit liver, it was found that penicillin G is hydrolyzed in rabbit liver to penicilloic acid. Perfusion for 2hours, with initial concentration of the penicillin in flowing fluid at 900γ/cc., resulted in the decrease of penicillin concentration to 250γ/cc. and formation of ca. 400γ/cc. of penicilloic acid. Formation of penicilloic acid was identified from paper electrophoresis and from Rf values in paper chromatography using butanol, isobutanol, or isoamyl alcohol, saturated with 0.2M phosphate buffer (pH 6.0), as a developing solvent. Coloration of the chromatogram utilized the reduction of arsenomolybdic acid to blue color and coloration of the spot to brown by spraying 0.1N ammonia water and silver nitrate.
Penicillin also changed to penicilloic acid on application of liver homogenate but the penicillin-decomposing enzyme is so rapidly inactivated that the liver must be homogenized under ice-cooling immediately after killing of the animal and reacted at once with penicillin. Optimal pH of this reaction is 6.9 and the reaction rate is proportional to the concentration of the homogenate used. No decomposition of penicillin occurred when the homogenate was heated at 100° for 3minutes. When liver homogenate and penicillin G were reacted, 3.2mg. of penicillin per 1g. wet weight of the liver was hydrolyzed and 3mg. of penicilloic acid was formed. Excess of penicillin did not inhibit this reaction. Ferric nitrate and calcium nitrate, which inhibit penicillinase of bacteria, do not inhibit hydrolysis of penicillin by liver homogenate and, therefore, penicillin-decomposing enzyme present in the liver is different in nature from bacterial penicillinase.