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肽的臭氧分解:酪氨酸和组氨酸残基氧化的产物结构及相对反应活性

Peptide ozonolysis: product structures and relative reactivities for oxidation of tyrosine and histidine residues.

作者信息

Lloyd Julie A, Spraggins Jeffrey M, Johnston Murray V, Laskin Julia

机构信息

Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA.

出版信息

J Am Soc Mass Spectrom. 2006 Sep;17(9):1289-98. doi: 10.1016/j.jasms.2006.05.009. Epub 2006 Jul 3.

Abstract

Angiotensin II (DRVYIHPF) and two analogs, (DRVYIAPA and DRVAIHPA), were used as model systems to study the ozonolysis of peptides containing tyrosine and histidine residues. The ESI mass spectrum of angiotensin II following exposure to ozone showed the formation of adducts containing one, three, and four oxygen atoms. CID and SID spectra of these adducts were consistent with formation of Tyr + O and His + 3O as expected from previous work with amino acids. However, several fragment ions observed in the CID and SID spectra suggested formation of a rather unexpected adduct, Tyr + 3O, and a small amount of the Phe + O adduct. These findings were confirmed by examining two angiotensin analogs. Exposure of DRVYIAPA to ozone resulted in the addition of either one or three oxygen atoms on Tyr, while DRVAIHPA showed only the addition of three oxygen atoms--all on His. Other noteworthy minor oxidation products were observed from these analogs including Tyr + 34 Da, His + 5 Da, His + 34 Da, and His + 82 Da. The reaction rates of the peptides with ozone were found to be similar: second-order rate coefficients are 274 +/- 3, 379 +/- 6, and 439 +/- 34 M(-1) s(-1) for DRVYIAPA, DRVAIHPA, and angiotensin II, respectively. The relative rates indicate (1) an isolated His residue has a slightly greater ozone reactivity than an isolated Tyr residue, and (2) the reaction rates of isolated residues are not additive when both residues are present in the same molecule.

摘要

血管紧张素II(DRVYIHPF)及其两种类似物(DRVYIAPA和DRVAIHPA)被用作模型系统,以研究含酪氨酸和组氨酸残基的肽的臭氧分解反应。暴露于臭氧后的血管紧张素II的电喷雾质谱显示形成了含一个、三个和四个氧原子的加合物。这些加合物的碰撞诱导解离(CID)和源内裂解(SID)光谱与酪氨酸加氧(Tyr + O)和组氨酸加三个氧(His + 3O)的形成一致,这与先前对氨基酸的研究预期相符。然而,在CID和SID光谱中观察到的几个碎片离子表明形成了一个相当意外的加合物——酪氨酸加三个氧(Tyr + 3O)以及少量的苯丙氨酸加氧(Phe + O)加合物。通过研究两种血管紧张素类似物证实了这些发现。DRVYIAPA暴露于臭氧会导致酪氨酸上添加一个或三个氧原子,而DRVAIHPA仅显示三个氧原子都加在了组氨酸上。从这些类似物中还观察到了其他值得注意的微量氧化产物,包括Tyr + 34 Da、His + 5 Da、His + 34 Da和His + 82 Da。发现这些肽与臭氧的反应速率相似:DRVYIAPA、DRVAIHPA和血管紧张素II的二级反应速率系数分别为274±3、379±6和439±34 M⁻¹ s⁻¹。相对反应速率表明:(1)孤立的组氨酸残基比孤立的酪氨酸残基具有稍高的臭氧反应活性;(2)当同一分子中同时存在这两个残基时,孤立残基的反应速率并非相加关系。

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