Katz E, Kamal F, Mason K
J Biol Chem. 1979 Jul 25;254(14):6684-90.
Radioisotopic experiments have revealed that free trans-4-hydroxy-L-proline is an intermediate synthesized from L-proline during formation of the peptide-bound cis-4-hydroxy-D-proline residue in the antibiotic, etamycin. This conclusion was based on the fact that 1) both radiolabeled L-proline and trans-4-hydroxy-L-proline are precursors of the bound D-imino acid as noted previously by Hook and Vining ((1973) J. Chem. Soc. Chem. Commun. 185-186; (1973) Can. J. Biochem. 51, 1630-1637), 2) the unlabeled trans isomer specifically inhibited the incorporation of radiolabel from proline into the antibiotic, 3) the 14C-hydroxyimino-acid was isolated from the intracellular pool and medium following incubations with L-[14C]proline during antibiotic biosynthesis and when etamycin synthesis was blocked by D-leucine. By means of chromatographic and enzymatic analyses, it was established that the free imino acid possesses the trans-L configuration.
放射性同位素实验表明，在抗生素埃他霉素中，游离的反式-4-羟基-L-脯氨酸是在肽结合的顺式-4-羟基-D-脯氨酸残基形成过程中由L-脯氨酸合成的中间体。这一结论基于以下事实：1）如Hook和Vining之前所指出的（（1973年）《化学学会化学通讯》185 - 186页；（1973年）《加拿大生物化学杂志》51卷，1630 - 1637页），放射性标记的L-脯氨酸和反式-4-羟基-L-脯氨酸都是结合的D-亚氨基酸的前体；2）未标记的反式异构体特异性地抑制了脯氨酸中放射性标记掺入抗生素；3）在抗生素生物合成过程中，用L-[14C]脯氨酸孵育后，以及当埃他霉素合成被D-亮氨酸阻断时，从细胞内池和培养基中分离出了14C-羟基亚氨基酸。通过色谱和酶分析确定，游离亚氨基酸具有反式-L构型。
