MECHANISM OF HUMAN NEUTROPHILS: LABILE INTERMEDIATES ALONG REACTION PATHWAY

我们证明了中性粒细胞几乎氧化了所有的氨基酸， 血浆中常见的酸转化为相应的醛类 高产量。 该反应由次氯酸（HOCl）介导， 髓过氧化物酶-H2 O2-Cl-系统产生的主要氧化剂 吞噬细胞 我们现在提出的证据的潜在机制， 这种反应，包括结构要求和反应 中间体形成。 利用质谱和同位素 标记的氨基酸，我们排除了氢原子的抽象， （-碳作为氨基酸过程中醛形成的初始事件 氧化，一种已知的电离辐射发生的途径。 醛 从氨基酸产生需要存在（-氨基 部分;（-和（-氨基酸在氧化后不形成醛， 髓过氧化物酶系统或HOCl，产生稳定的 一氯胺代替。 紫外差光谱法、HPLC和 多核（1H，15 N）NMR光谱表明， β-氨基酸转化为醛开始于β-氨基酸的生成， 一种不稳定的（-）-一氯胺，随后分解产生 醛。 前体-产物之间的关系（-氨基酸和 通过紫外分光光度法测定了（-单氯胺）、（-单氯胺）和醛的含量。 反应中间体的HPLC纯化和随后的1H和 15 N NMR光谱。 总的来说，这些结果详细说明了 反应机理和反应过程中产生的中间产物 通过髓过氧化物酶产生的HOCl将氨基酸转化为醛。

We demonstrated 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 multinuclear (1H, 15N) NMR spectroscopy establ ished 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.