Pecci L, Costa M, Antonucci A, Montefoschi G, Cavallini D
Dipartimento di Scienze Biochimiche "A. Rossi Fanelli" and, Università di Roma "La Sapienza,", Rome, Italy.
Biochem Biophys Res Commun. 2000 Apr 21;270(3):782-6. doi: 10.1006/bbrc.2000.2489.
The methylene blue photosensitized oxidation of cysteine sulfinic acid is investigated. Enhancement of the oxygen consumption rate in deuterium oxide suggests the involvement of singlet oxygen ((1)O(2)) in oxidation. Addition of the (1)O(2) quencher azide produced an unusual enhancement of the oxidation rate of all the sulfinates assayed. It is assumed that azide works as a one-electron carrier between (1)O(2) and the sulfur compounds. Analyses of the products indicate that the photochemical oxidation of cysteine sulfinic acid proceeds through two simultaneous mechanisms. The Type II (singlet oxygen) mechanism is responsible for oxidation of the sulfinic group to the sulfonic group with production of cysteic acid, stable to the photooxidation system, whereas the Type I (electron transfer) mechanism is involved in the degradation of cysteine sulfinic acid to acetaldehyde. Other products detected were ammonia, sulfate, and hydrogen peroxide which account for the degradation of cysteine sulfinic acid and for the excess of oxygen consumption detected during the oxidative reaction.
研究了亚甲基蓝光敏氧化半胱氨酸亚磺酸的过程。氧化氘中耗氧速率的提高表明单线态氧((1)O(2))参与了氧化反应。添加(1)O(2)猝灭剂叠氮化物使所有被测亚磺酸盐的氧化速率出现异常提高。据推测，叠氮化物在(1)O(2)和硫化合物之间充当单电子载体。产物分析表明，半胱氨酸亚磺酸的光化学氧化通过两种同时发生的机制进行。II型（单线态氧）机制负责将亚磺酸基团氧化为磺酸基团，生成对光氧化系统稳定的半胱氨酸，而I型（电子转移）机制则参与半胱氨酸亚磺酸降解为乙醛的过程。检测到的其他产物是氨、硫酸盐和过氧化氢，它们解释了半胱氨酸亚磺酸的降解以及氧化反应中检测到的过量耗氧现象。
