细叶香豌豆（Lathyrus tingitanus L.）对嘧啶基氨基酸β-氨基丙腈的生物合成
Biosynthesis of the pyrimidinyl amino acid lathyrine by Lathyrus tingitanus L.
作者信息
Brown E G, Al-Baldowi N F
出版信息
Biochem J. 1977 Jun 15;164(3):589-94. doi: 10.1042/bj1640589.
The biosynthesis of the pyrimidinyl amino acid lathyrine by seedlings of Lathyrus tingitanus L. was shown to be stimulated by uracil. [6(-14)C]Orotate, [2(-14)C]uracil and [3(-14)C]serine were incorporated into lathyrine; the incorporation of [6(-14)C]orotate was substantially decreased in the presence of uracil. Chemical degradation to locate the 14C incorporated from labelled precursors showed that 90% of the radioactivity incorporated into lathyrine from [3(-14)C]serine could be recovered in the alanine side chain. Over 80% of the radioactivity incorporated from [2(-14)C]uracil was shown to be located in C-2 of lathyrine. It is concluded that under the conditions studied, lathyrine arises from a preformed pyrimidine arising via the orotate pathway. Paradoxically, it was also possible to confirm previous reports that radioactivity from L-[guanidino-14C]homoarginine is incorporated into lathyrine and gamma-hydroxyhomoarginine. However, as homoarginine and gamma-hydroxyhomoarginine are also both labelled by [2(-14)C]uracil, it is suggested that they are products of the ring-opening of lathyrine and that reversibility of this process accounts, at least in part, for their observed experimental incorporation into lathyrine.
研究表明，来自细叶山黧豆（Lathyrus tingitanus L.）幼苗的嘧啶基氨基酸β-草酰氨基-L-α,β-二氨基丙酸（lathyrine）的生物合成受到尿嘧啶的刺激。[6(-14)C]乳清酸、[2(-14)C]尿嘧啶和[3(-14)C]丝氨酸被掺入到β-草酰氨基-L-α,β-二氨基丙酸中；在尿嘧啶存在的情况下，[6(-14)C]乳清酸的掺入量大幅下降。通过化学降解来定位从标记前体掺入的14C，结果表明，从[3(-14)C]丝氨酸掺入到β-草酰氨基-L-α,β-二氨基丙酸中的放射性，有90%可以在丙氨酸侧链中回收。已表明，从[2(-14)C]尿嘧啶掺入的放射性，超过80%位于β-草酰氨基-L-α,β-二氨基丙酸的C-2位。得出的结论是，在所研究的条件下，β-草酰氨基-L-α,β-二氨基丙酸源自通过乳清酸途径形成的预先存在的嘧啶。矛盾的是，也有可能证实先前的报道，即来自L-[胍基-14C]高精氨酸的放射性被掺入到β-草酰氨基-L-α,β-二氨基丙酸和γ-羟基高精氨酸中。然而，由于高精氨酸和γ-羟基高精氨酸也都被[2(-14)C]尿嘧啶标记，因此有人提出它们是β-草酰氨基-L-α,β-二氨基丙酸开环的产物，并且这一过程的可逆性至少部分解释了它们在实验中被观察到掺入到β-草酰氨基-L-α,β-二氨基丙酸中的现象。
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