{"title":"髓过氧化物酶和牛肉甲状腺对酪氨酸的碘化作用。自由基的可能参与","authors":"Cecil C. Yip, Linda D. Hadley","doi":"10.1016/0926-6593(66)90033-6","DOIUrl":null,"url":null,"abstract":"<div><p></p><ul><li><span>1.</span><span><p>1. The oxidation of sulfite, measured by the uptake of oxygen, was employed to detect the formation of free radicals in the iodination of tyrosine by myeloperoxidase in the presence of added H<sub>2</sub>O<sub>2</sub>.</p></span></li><li><span>2.</span><span><p>2. The uptake of oxygen was dependent on sulfite, tyrosine and myeloperoxidase. Tyrosine could be replaced by monoiodotyrosine, diiodotyrosine, 4-hydroxy-3,5-diiodophenylacetic acid or 4-hydroxy-3,5-diiodobenzaldehyde but not by thyroglobulin, phenylacetic acid, phenylalanine or iodide. Iodide was inhibitory.</p></span></li><li><span>3.</span><span><p>3. The oxidation of sulfite under these conditions was affected by pH and had an optimal range between pH 5 and 6.5.</p></span></li><li><span>4.</span><span><p>4. Sulfite and bisulfite inhibited completely the iodination of tyrosine and of thyroglobulin by myeloperoxidase in the presence of added H<sub>2</sub>O<sub>2</sub>. Sulfate was without effect.</p></span></li><li><span>5.</span><span><p>5. The iodination of tyrosine by myeloperoxidase in the presence of added H<sub>2</sub>O<sub>2</sub> showed the same pH optimum as the oxidation of sulfite.</p></span></li><li><span>6.</span><span><p>6. A concentrated solubilized preparation of beef thyroid tissues, which catalyzed the peroxidation of <span><math><mtext>o-</mtext><mtext>dianisidine</mtext></math></span> and the iodination of tyrosine, could not substitute effectively for myeloperoxidase in the oxidation of sulfite. However, the iodination of tyrosine by this enzyme preparation was inhibited by sulfite and bisulfite.</p></span></li><li><span>7.</span><span><p>7. These results are discussed in relation to a free radical reaction mechanism involved in the synthesis of iodotyrosines by myeloperoxidase and by the beef thyroid preparation.</p></span></li></ul></div>","PeriodicalId":100160,"journal":{"name":"Biochimica et Biophysica Acta (BBA) - Enzymology and Biological Oxidation","volume":null,"pages":null},"PeriodicalIF":0.0000,"publicationDate":"1966-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0926-6593(66)90033-6","citationCount":"18","resultStr":"{\"title\":\"The iodination of tyrosine by myeloperoxidase and beef thyroids. The possible involvement of free radicals\",\"authors\":\"Cecil C. Yip, Linda D. Hadley\",\"doi\":\"10.1016/0926-6593(66)90033-6\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p></p><ul><li><span>1.</span><span><p>1. The oxidation of sulfite, measured by the uptake of oxygen, was employed to detect the formation of free radicals in the iodination of tyrosine by myeloperoxidase in the presence of added H<sub>2</sub>O<sub>2</sub>.</p></span></li><li><span>2.</span><span><p>2. The uptake of oxygen was dependent on sulfite, tyrosine and myeloperoxidase. Tyrosine could be replaced by monoiodotyrosine, diiodotyrosine, 4-hydroxy-3,5-diiodophenylacetic acid or 4-hydroxy-3,5-diiodobenzaldehyde but not by thyroglobulin, phenylacetic acid, phenylalanine or iodide. Iodide was inhibitory.</p></span></li><li><span>3.</span><span><p>3. The oxidation of sulfite under these conditions was affected by pH and had an optimal range between pH 5 and 6.5.</p></span></li><li><span>4.</span><span><p>4. Sulfite and bisulfite inhibited completely the iodination of tyrosine and of thyroglobulin by myeloperoxidase in the presence of added H<sub>2</sub>O<sub>2</sub>. Sulfate was without effect.</p></span></li><li><span>5.</span><span><p>5. The iodination of tyrosine by myeloperoxidase in the presence of added H<sub>2</sub>O<sub>2</sub> showed the same pH optimum as the oxidation of sulfite.</p></span></li><li><span>6.</span><span><p>6. A concentrated solubilized preparation of beef thyroid tissues, which catalyzed the peroxidation of <span><math><mtext>o-</mtext><mtext>dianisidine</mtext></math></span> and the iodination of tyrosine, could not substitute effectively for myeloperoxidase in the oxidation of sulfite. However, the iodination of tyrosine by this enzyme preparation was inhibited by sulfite and bisulfite.</p></span></li><li><span>7.</span><span><p>7. These results are discussed in relation to a free radical reaction mechanism involved in the synthesis of iodotyrosines by myeloperoxidase and by the beef thyroid preparation.</p></span></li></ul></div>\",\"PeriodicalId\":100160,\"journal\":{\"name\":\"Biochimica et Biophysica Acta (BBA) - Enzymology and Biological Oxidation\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":0.0000,\"publicationDate\":\"1966-09-12\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://sci-hub-pdf.com/10.1016/0926-6593(66)90033-6\",\"citationCount\":\"18\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Biochimica et Biophysica Acta (BBA) - Enzymology and Biological Oxidation\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/0926659366900336\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"\",\"JCRName\":\"\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Biochimica et Biophysica Acta (BBA) - Enzymology and Biological Oxidation","FirstCategoryId":"1085","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/0926659366900336","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
The iodination of tyrosine by myeloperoxidase and beef thyroids. The possible involvement of free radicals
1.
1. The oxidation of sulfite, measured by the uptake of oxygen, was employed to detect the formation of free radicals in the iodination of tyrosine by myeloperoxidase in the presence of added H2O2.
2.
2. The uptake of oxygen was dependent on sulfite, tyrosine and myeloperoxidase. Tyrosine could be replaced by monoiodotyrosine, diiodotyrosine, 4-hydroxy-3,5-diiodophenylacetic acid or 4-hydroxy-3,5-diiodobenzaldehyde but not by thyroglobulin, phenylacetic acid, phenylalanine or iodide. Iodide was inhibitory.
3.
3. The oxidation of sulfite under these conditions was affected by pH and had an optimal range between pH 5 and 6.5.
4.
4. Sulfite and bisulfite inhibited completely the iodination of tyrosine and of thyroglobulin by myeloperoxidase in the presence of added H2O2. Sulfate was without effect.
5.
5. The iodination of tyrosine by myeloperoxidase in the presence of added H2O2 showed the same pH optimum as the oxidation of sulfite.
6.
6. A concentrated solubilized preparation of beef thyroid tissues, which catalyzed the peroxidation of and the iodination of tyrosine, could not substitute effectively for myeloperoxidase in the oxidation of sulfite. However, the iodination of tyrosine by this enzyme preparation was inhibited by sulfite and bisulfite.
7.
7. These results are discussed in relation to a free radical reaction mechanism involved in the synthesis of iodotyrosines by myeloperoxidase and by the beef thyroid preparation.
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