HUMAN NEUTROPHILS EMPLOY MYELOPEROXIDASE H2O2 CL SYS TO OXIDIZE

在随附的手稿中，我们证明了中性粒细胞 氧化几乎所有的氨基酸通常发现在血浆中的一个 以高产率合成相应的醛类。 反应 介导的次氯酸（HOCl），主要氧化剂产生的 吞噬细胞的髓过氧化物酶-H_2O_2-Cl-系统。 我们现在提出 这种反应的潜在机制的证据，包括 结构要求和形成的反应中间体。 利用 质谱和同位素标记的氨基酸我们排除了 氢原子从（-碳）中提取作为初始事件， 在氨基酸氧化过程中形成醛，这是一种已知的 发生在电离辐射中。 从氨基酸生成醛 需要存在（-氨基部分;（-和（-氨基酸确实 在被髓过氧化物酶系统氧化时不形成醛 或HOCl，生成稳定的一氯胺。 紫外差 光谱、HPLC和多核（1H，15 N）NMR光谱 确定了（-氨基酸转化为醛开始 并产生不稳定的（-）-一氯胺，随后 分解产生醛。 前体-产品关系 在（-氨基酸和（-一氯胺之间，和（-一氯胺和 通过反应的HPLC纯化确认醛 中间体和随后的1H和15 N NMR光谱。 总的来说，这些结果详细说明了化学机理和反应 在将氨基酸转化为 醛通过髓过氧化物酶产生的HOCl。

In the accompanying manuscript we demonstrate that neutrophils oxidize nearly all of the amino acids commonly found in plasma to a corresponding family of aldehydes in high yield. The reaction is mediated by hypochlorous acid (HOCl), the major oxidant generated by the myeloperoxidase-H2O2-Cl- system of phagocytes. We now present evidence for the underlying mechanism of this reaction, including the structural requirements and reaction intermediates formed. Utilizing mass spectrometry and isotopically labeled amino acids we rule out hydrogen atom abstraction from the (-carbon as the initial event in aldehyde formation during amino acid oxidation, a pathway known to occur with ionizing radiation. Aldehyde generation from amino acids required the presence of an (-amino moiety; (- and (-amino acids did not form aldehydes upon oxidation by either the myeloperoxidase system or HOCl, generating stable monochloramines instead. UV difference spectroscopy, HPLC and multin uclear (1H , 15N) NMR spectroscopy established that the conversion of (-amino acids into aldehydes begins with generation of an unstable (-monochloramine, which subsequently decomposes to yield an aldehyde. Precursor-product relationships between (-amino acid and (-monochloramine, and (-monochloramine and aldehyde were confirmed by HPLC purification of the reaction intermediate and subsequent 1H and 15N NMR spectroscopy. Collectively, these results detail the chemical mechanism and reaction intermediates generated during conversion of amino acids into aldehydes by myeloperoxidase-generated HOCl.