Møller B L, Conn E E
J Biol Chem. 1979 Sep 10;254(17):8575-83.
The following compounds were tested as early intermediates in the conversion of tyrosine to p-hydroxymandelonitrile by a microsomal preparation from dark grown sorghum seedlings: p-hydroxyphenylacetamide, 1-nitro-2-p-hydroxyphenylethane, p-hydroxyphenyl-pyruvic acid oxime, tyramine, N-hydroxytyramine, and N-hydroxytyrosine. Of these, only N-hydroxytyrosine was metabolized to p-hydroxymandelonitrile. N-Hydroxytyrosine was produced from L-[U-14C]tyrosine in tracer experiments when unlabeled N-hydroxytyrosine was added as a trap. These data indicate N-hydroxytyrosine as the first intermediate in the biosynthesis of dhurrin, the cyanogenic glucoside of sorghum, and represent the first demonstration of the formation of an alpha-N-hydroxy-amino acid in a biological system. The enzyme system involved in this reaction was partially characterized with respect to substrate specificity and the effect of various inhibitors. The enzyme was shown to have properties different than those reported for the mammalian enzyme system(s) involved in the N-hydroxylation of amine drugs. The possible involvement of N-hydroxyamino acids in the biosynthesis of other secondary plant products is discussed.
对羟基苯乙酰胺、1-硝基-2-对羟基苯乙烷、对羟基苯丙酮酸肟、酪胺、N-羟基酪胺和N-羟基酪氨酸。其中，只有N-羟基酪氨酸代谢为对羟基苯乙腈。在示踪实验中，当加入未标记的N-羟基酪氨酸作为捕获剂时，L-[U-14C]酪氨酸产生了N-羟基酪氨酸。这些数据表明N-羟基酪氨酸是高粱生氰糖苷蜀黍苷生物合成中的第一个中间体，并且代表了在生物系统中α-N-羟基氨基酸形成的首次证明。针对该反应所涉及的酶系统，就底物特异性和各种抑制剂的作用进行了部分表征。结果表明该酶具有与报道的参与胺类药物N-羟基化的哺乳动物酶系统不同的特性。还讨论了N-羟基氨基酸在其他次生植物产物生物合成中的可能作用。
