【摘要】 从人工感染的家兎中取得日本血吸虫成虫,制成匀浆后在37℃测定鸟氨酸转氨酶活力,底物L-鸟氨酸及α-酮戊二酸的浓度各为0.017M,pH8.O。测定结果用微克分子/ 毫克氮/小时表示,测得酶活力的平均值雄虫为33.9,雌虫为29.0。此酶的最适pH为8.O—8.2。在对此测定中合抱虫的鸟氨酸转氨酶活力为谷氨酸丙酮酸转氨酸活力的1.5倍,谷氨酸草酰乙酸转氨酶活力的2.4倍。当用鸟氨酸分别与α-酮戊二酸、丙酮酸、草酰乙酸及乙醛酸进行测定时,测得的酶活力比值依次为100:6.2:1.8:4.2。磷酸吡哆醛能增高酶活力,羟胺则使之降低。氯化铜及对氯汞苯甲酸具有很强的抑制作用,在2×10^-5M的浓度下前者抑制78.5%,后者抑制31.6%。正缬氨酸及缬氨酸对此酶的抑制作用是竞争性的,当底物鸟氨酸的浓度减低时,抑制作用增强。南瓜子氨酸的抑制是非竞争性的,在O.017M的浓度下抑制酶活力29.5%。酒石酸锑钾(10^-3M)及呋喃丙胺(10^-4M)对酶活力无影响。在日本血吸虫中测不出精氨酸转氨酶的存在,以精氨酸为底物作转氨酶测定时所产生的谷氨酸是由于精氨酸酶和鸟氨酸转氨酶相继作用的结果。更多还原

【Abstract】 Adult worms of Schistosoma japonicum, collected from experimentally infected rabbits, were homogenized and the homogenate was incubated with 0.017M L-ornithine and 0.017M α-ketoglutarate at 37℃, the pH of the medium was 8.0. The ornithine transaminase activity was expressed in micromoles of glutamic acid produced per mg. nitrogen per hour. The average values of enzymic activity were found to be 33.9 for male worms and 29.0 for female worms. The pH optimum for the enzyme was 8.0-8.2. Using the homogenate of paired worms, the activities of ornithine transaminase, glutamic-pyruvic transaminase （GPT） and glutamic-oxaloacetio transaminase （GOT） were determined respectively. The activity of the first enzyme was 1.5 times greater than that of GPT and 2.4 times greater than that of GOT. When α-ketoglutarate, pyruvate, oxaloacetate or glyoxalate was used as one of the substrates and L-ornithine as the other, the ratio of enzymic activities observed was 100:6.2:1.8:4.2. The worm ornithine transaminase was activated by pyridoxal phosphate and depressed by hydroxylamine. Cupric chloride and p-chloromercu-ribenzoate had a notable inhibitory effect, at 2×10^-5M they caused 78.5% and 31.6% inhibition respectively. Norvaline and valine exhibited a competitive inhibition, its action increased significantly as the concentration of L-ornithine was decreased. Inhibition by cucurbitine was noncompetitive, 0.017M of this amino acid inhibited 30% of the enzymic activity. 10^-3M tartar emetic and 10^-4 M furapromidium （F-30066） did not show any effect. Arginine transaminase could not be detected in Schistosoma japonicum by the present method. When the homogenate was incubated with arginine and α-ketoglutarate, the glutamic acid produoed is most likely the result of the combined actions of arginase and ornithine transaminase.更多还原