In vivo regulation of de novo methionine biosynthesis in a higher plant (lemna).
In vivo regulation of de novo methionine biosynthesis in a higher plant (lemna).
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高等植物（浮萍）从头蛋氨酸生物合成的体内调节。
DOI：
10.1104/pp.77.2.450
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发表时间：
1985
期刊：
影响因子：
7.4
通讯作者：
A. Datko
中科院分区：
文献类型：
--
作者：
J. Giovanelli;S. Mudd;A. Datko
向生长中的浮萍施用蛋氨酸对蛋白质半胱氨酸中硫酸硫的积累基本上没有影响，但将胱硫醚及其产物（高半胱氨酸、蛋氨酸、S-甲基甲硫氨酸锍盐、S-腺苷甲硫氨酸和S-腺苷高半胱氨酸）的积累减少至对照植物的21%，这表明蛋氨酸在胱硫醚合成中调节其自身的从头合成。蛋氨酸仅导致蔗糖碳在胱硫醚和产物的4碳部分中的积累略有减少（至对照植物的80%）。这一观察结果令人费解，因为胱硫醚的合成是通过掺入等量的硫（来自半胱氨酸）和 4-碳部分（来自 O-磷酸高丝氨酸）进行的。 Lemna (Giovanelli, Datko, Mudd, Thompson 1983 Plant Physiol 71:319-326)中的论证解决了明显的不一致，即甲硫氨酸4-碳部分的从头合成不仅通过O-磷酸高丝氨酸的已建立的转硫途径发生，而且还通过5'-甲硫腺苷的核糖部分发生。现在很清楚，通过转硫作用对硫（和 4-碳部分）通量的更准确评估是通过在胱硫醚及其产物中积累的 (35)SO(4) (2-) 中产生的 (35)S 的量来提供的，而不是通过 (14)C 的相应测量来提供的。因此，这些研究明确地证明，在高等植物中，蛋氨酸确实反馈调节其自身在体内的从头合成，并且胱硫醚合成是这种调节的场所。
Administration of methionine to growing Lemna had essentially no effect on accumulation of sulfate sulfur in protein cysteine, but decreased accumulation into cystathionine and its products (homocysteine, methionine, S-methylmethioninesulfonium salt, S-adenosylmethionine, and S-adenosylhomocysteine) to as low as 21% that of control plants, suggesting that methionine regulates its own de novo synthesis at cystathionine synthesis. Methionine caused only a slight reduction (to 80% that of control plants) in the accumulation of sucrose carbon into the 4-carbon moieties of cystathionine and products. This observation was puzzling since cystathionine synthesis proceeds by incorporation of equivalent amounts of sulfur (from cysteine) and 4-carbon moieties (from O-phosphohomoserine). The apparent inconsistency was resolved by the demonstration in Lemna (Giovanelli, Datko, Mudd, Thompson 1983 Plant Physiol 71: 319-326) that de novo synthesis of the methionine 4-carbon moiety occurs not only via the established transsulfuration route from O-phosphohomoserine, but also via the ribose moiety of 5'-methylthioadenosine. It is now clear that the more accurate assessment of the flux of sulfur (and 4-carbon moieties) through transsulfuration is provided by the amount of (35)S from (35)SO(4) (2-) that accumulates in cystathionine and its products, rather than by the corresponding measurements with (14)C. These studies therefore unequivocally demonstrate in higher plants that methionine does indeed feedback regulate it own de novo synthesis in vivo, and that cystathionine synthesis is a locus for this regulation.