Interrelationships between gluconeogenesis and ureogenesis in isolated hepatocytes.
Interrelationships between gluconeogenesis and ureogenesis in isolated hepatocytes.
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离体肝细胞糖异生和尿素生成之间的相互关系。
DOI：
10.1016/s0021-9258(17)38074-2
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发表时间：
1978
期刊：
影响因子：
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通讯作者：
J. Williamson
中科院分区：
文献类型：
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作者：
A. Meijer;J. Gimpel;G. Deleeuw;M. Tischler;J. Tager;J. Williamson
来自宾夕法尼亚大学生物化学和生物物理学系，费城，宾夕法尼亚19104和阿姆斯特丹大学生物化学实验室，BCP Jansen Institute，Plantage Muidergracht 12，Amsterdam，The Netherlands或，-环丝氨酸（5 - 10 mvl），当加入到分离的肝细胞中时，显示主要在胞质溶胶中抑制天冬氨酸氨基转移酶。在低浓度（0.1至0.2 μ），它选择性抑制丙氨酸氨基转移酶。氨基氧乙酸（0.5 mu）不可逆地抑制所有转氨酶活性，前提是在底物添加前添加抑制剂。无论是环丝氨酸，也不aminoxyacetate引起明显的抑制从丙酮酸，但这两种抑制剂大大降低从乳酸的amineogenesis。这些观察结果证实了早期的发现，苹果酸从线粒体流出占主导地位的丙酮酸作为葡萄糖前体，而天冬氨酸流出占主导地位的乳酸作为底物。通过分离的肝细胞从氨合成尿素受到内源性鸟氨酸的限制。半最大刺激尿素合成丙酮酸的存在下，获得0.5亩外源性鸟氨酸。对瓜氨酸积累的测量表明：（a）氨甲酰磷酸的形成不是限速的;（6）氨基琥珀酸合成酶对瓜氨酸的表观K值约为1.5 μ。在存在鸟氨酸和乳酸或丙酮酸的情况下，尿素的形成受到氨基琥珀酸合成酶活性的限制。氨氧乙酸完全抑制尿素合成，但在很大程度上不受环丝氨酸。这些数据表明，尿素合成所需的天冬氨酸必须在线粒体中产生。天冬氨酸的积累表明，其形成速率并不限制尿素的合成。在没有鸟氨酸的情况下加入环丝氨酸刺激氨形成尿素。这种效应是由于抑制鸟氨酸转氨酶而导致细胞内瓜氨酸水平升高所致。向油酸盐孵育的肝细胞中添加氨 * 这项工作得到了美国公共卫生署授予JRW的Grant AM 15120和荷兰纯科学研究组织（Z. W. 0.）的情况。在荷兰化学研究基金会（S. 0. N.）。这篇文章的出版费用部分由版面费支付。因此，根据18 USC第1734条，本文必须在此标记为“广告”，以表明这一事实。荷兰纯科学研究组织提供的访问美利坚合众国研究金（ZW 0.）。
From the Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104 and the Laboratory of Biochemistry, University of Amsterdam, BCP Jansen Institute, Plantage Muidergracht 12, Amsterdam, The Netherlands or,-Cycloserine (5 to 10 mvl), when added to isolated hepatocytes, is shown to inhibit aspartate aminotransferase predominantly in the cytosol. At low concentrations(0.1 to 0.2 mu) it selectively inhibits alanine aminotransferase. Aminooxyacetate(0.5 mu) irreversibly inhibits all transaminase activity provided the inhibitor is added prior to substrate addition. Neither cycloserine nor aminooxyacetate caused appreciable inhibition of gluconeogenesis from pyruvate, but both inhibitors greatly decreased gluconeogenesis from lactate. These observations confirm earlier findings that malate efflux from mitochondria predominates with pyruvate as glucose precursor while aspartate efflux predominates with lactate as substrate. Urea synthesis from ammonia by isolated hepatocytes was limited by endogenous ornithine. Half-maximal stimulation of urea synthesis in the presence of pyruvate was obtained with 0.5 mu exogenous ornithine. Measurements of citrulline accumulation showed (a) that carbamyl phosphate formation was not rate-limiting and (6) that the apparent K, of argininosuccinate synthetase for citrulline was about 1.5 mu. Urea formation in the presence of ornithine and either lactate or pyruvate was limited by the activity of argininosuccinate synthetase. Urea synthesis was completely inhibited by aminooxyacetate, but was largely unaffected by cycloserine. These data show that aspartate required for urea synthesis must be generated in the mitochondria. Accumulation of aspartate showed that its rate of formation was not limiting for urea synthesis. Cycloserine addition in the absence of ornithine stimulated urea formation from ammonia. This effect was caused by an increase of intracellular citrulline levels because of inhibition of ornithine transaminase. Ammonia addition to hepatocytes incubated with oleate* This work was supported by Grant AM 15120 to JRW from the United States Public Health Service and by a Grant to JMT from the Netherlands Organization for Pure Scientific Research (Z. W. 0.) under auspices of the Netherlands Foundation for Chemical Research (S. 0. N.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 USC Section 1734 solely to indicate this fact. $ Recipient of a fellowship for a visit to the United States of America from the Netherlands Organization for Pure Scientific Research (ZW 0.).