Chassaigne H, Vacchina V, Kutchan T M, Zenk M H
Institut für Pflanzenbiochemie, Halle, Germany.
Phytochemistry. 2001 Apr;56(7):657-68. doi: 10.1016/s0031-9422(00)00489-1.
An analytical strategy based on the sensitivity of electrospray tandem mass spectrometry following a simplified and reproducible sample preparation procedure was evaluated for the determination of Cd-induced phytochelatins (PC) and related peptides in four maize varieties. In addition to the three known families of PC (PC, desGly-PC and iso-PC(Glu)) that were observed, novel PC and desGly-PC homologues lacking the N-terminal gamma-linked Glu were isolated from maize root extracts for the first time. Additionally the complete sequence of iso-PC3(Glu) was determined by tandem mass spectrometry. Peptides obtained in vivo and in vitro as the result of the reaction of glutathione with the enzyme phytochelatin synthase were compared. Minor forms detected from in vitro reactions include compounds with intramolecular or intermolecular disulfide bonds resulting from the oxidation of SH groups, phytochelatin homologues lacking the N-terminal gamma-linked Glu, and new PC-related peptides with a Cys-Cys motif. Since peptides lacking a gammaGlu residue could be generated as artifacts in electrospray mass spectrometry, the application of capillary electrophoresis with online electrospray mass spectrometry allowed the separation and detection of such peptides as endogenous molecules present in planta and as products of in vitro reactions.
采用一种基于简化且可重复的样品制备程序后的电喷雾串联质谱灵敏度的分析策略，对四个玉米品种中镉诱导的植物螯合肽（PC）及相关肽进行了测定。除了观察到的已知的三个PC家族（PC、去甘氨酸-PC和异-PC（Glu））外，首次从玉米根提取物中分离出了缺少N端γ-连接谷氨酸的新型PC和去甘氨酸-PC同系物。此外，通过串联质谱法确定了异-PC3（Glu）的完整序列。比较了谷胱甘肽与植物螯合肽合酶反应在体内和体外产生的肽。体外反应检测到的次要形式包括因SH基团氧化产生的具有分子内或分子间二硫键的化合物、缺少N端γ-连接谷氨酸的植物螯合肽同系物，以及具有半胱氨酸-半胱氨酸基序的新的PC相关肽。由于缺少γ-谷氨酸残基的肽可能在电喷雾质谱中作为假象产生，因此采用毛细管电泳与在线电喷雾质谱联用技术，能够分离和检测此类肽，它们作为植物体内存在的内源性分子以及体外反应的产物。
