正常和糖尿病大鼠肝脏磷酸烯醇丙酮酸羧激酶活性对喹啉酸抑制和亚铁离子激活的反应。

Responses of hepatic phosphoenolypyruvate carboxykinase activities from normal and diabetic rats to quinolinate inhibition and ferrous ion activation.

作者信息

Maxwell J R, Ray P D

出版信息

Biochim Biophys Acta. 1980 Jul 10;614(1):163-72. doi: 10.1016/0005-2744(80)90177-1.

DOI:10.1016/0005-2744(80)90177-1

PMID:7397200

Abstract

Phosphoenolpyruvate carboxykinase (GTP:oxaloacetate carboxy-lyase (transphosphorylating), EC 4.1.1.32) from tryptophan-treated normal rats, when assayed immediately after preparation is not activated by Fe2+ but is inhibited 65% by 2.0 mM quinolinate whether or not Fe2+ is present. As time of storage increases, the enzyme's sensitivity to Fe2+ activation returns as does the ability of quinolinate to more effectively inhibit the Fe2+-activated enzyme. 2. Phosphoenolpyruvate carboxykinase from NaCl- and tryptophan-treated diabetic rats is activated about 2-fold by 20 microM Fe2+. Quinolinate (2.0 mM) inhibits the Fe2+-activated enzyme 65% compared to 20% inhibition of the non-Fe2+-activated enzyme. In these respects, the enzyme from NaCl- and tryptophan-treated diabetic rats acts in vitro just like the enzyme from NaCl-treated normal rats and unlike the enzyme from tryptophan-treated normal rats. Thus, the inability of tryptophan and quinolinate to inhibit gluconeogenesis and to alter the assayable activity of phosphoenolpyruvate carboxykinase from diabetic rats in vivo is inconsistent with quinolinate's ability to inhibit the enzyme in vitro. 3. Quinolinate's inhibition of phosphoenolpyruvate carboxykinase from NaCl, tryptoiphan-treated normal and diabetic rats is of a 'mixed' nature. 4. Hepatic cytosolic phosphoenolpyruvate carboxykinases from fasted normal guinea pigs, pigeons, and rabbits are activated 2-3-fold by Fe2+ and inhibition by quinolinate in the presence of Fe2+ ranges from 65-75% compared to no inhibition without Fe2+. Mitochondrial carboxykinases from these three species are only activated 20-30% by Fe2+, although quinolinate, which is ineffective as an inhibitor in the absence of Fe2+, inhibits the enzymes 40-50% in the presence of Fe2+.

摘要

用色氨酸处理过的正常大鼠的磷酸烯醇式丙酮酸羧激酶（GTP：草酰乙酸羧基裂解酶（转磷酸化），EC 4.1.1.32），在制备后立即进行测定时，不会被Fe²⁺激活，但无论Fe²⁺是否存在，都会被2.0 mM喹啉酸抑制65%。随着储存时间的增加，该酶对Fe²⁺激活的敏感性恢复，喹啉酸更有效地抑制Fe²⁺激活酶的能力也恢复。2. 用NaCl和色氨酸处理过的糖尿病大鼠的磷酸烯醇式丙酮酸羧激酶被20 μM Fe²⁺激活约2倍。喹啉酸（2.0 mM）抑制Fe²⁺激活的酶65%，相比之下，对未被Fe²⁺激活的酶的抑制率为20%。在这些方面，用NaCl和色氨酸处理过的糖尿病大鼠的酶在体外的作用方式与用NaCl处理过的正常大鼠的酶相同，与用色氨酸处理过的正常大鼠的酶不同。因此，色氨酸和喹啉酸在体内无法抑制糖异生以及改变糖尿病大鼠磷酸烯醇式丙酮酸羧激酶的可测定活性，这与喹啉酸在体外抑制该酶的能力不一致。3. 喹啉酸对用NaCl、色氨酸处理过的正常大鼠和糖尿病大鼠的磷酸烯醇式丙酮酸羧激酶的抑制作用具有“混合”性质。4. 禁食的正常豚鼠、鸽子和兔子的肝细胞质磷酸烯醇式丙酮酸羧激酶被Fe²⁺激活2 - 3倍，在有Fe²⁺存在的情况下，喹啉酸的抑制率为65 - 75%，而在没有Fe²⁺时则无抑制作用。这三个物种的线粒体羧激酶仅被Fe²⁺激活20 - 30%，尽管喹啉酸在没有Fe²⁺时作为抑制剂无效，但在有Fe²⁺存在时可抑制该酶40 - 50%。