{"title":"Kinetics of IMP:NAD+ oxidoreductase in serum of normal Iraqi individuals.","authors":"S A Al-Mudhaffar, M Al-Ubaidi","doi":"","DOIUrl":null,"url":null,"abstract":"<p><p>The general kinetic parameters of IMP:NAD+ oxidoreductase, were investigated at 37 degrees C in normal human serum. These included substrate - velocity relationship, Km (IMP), Km (NAD), as well as the effect of temperature and pH on the kinetics of the reaction. Optimum conditions of IMP, NAD+ oxidoreductase in serum of normal Iraqi individuals at 37 degrees C were investigated. The optimum IMP concentration was found to be 0.6166 mM and the optimum NAD+ concentration was 6.28 mM, while the optimum pH for the reaction was found to be 8.3. The enzyme shows low stability even when the sera were incubated at low temperature. The activity of the enzyme is proportional to the serum concentration and its optimal temperature for the reaction was 37 degrees C. The enzyme was found to be inhibited by XMP, GMP competitively with Ki values of 0.0724 mM and 0.1583 mM respectively. The inhibition by thyroid hormone (T4) was studied giving a Ki value of 2.25 X 10(-6) mM. The mechanism of enzyme action was found to follow ordered sequential mechanism.</p>","PeriodicalId":8818,"journal":{"name":"Biochemistry and experimental biology","volume":"16 1","pages":"87-97"},"PeriodicalIF":0.0000,"publicationDate":"1980-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Biochemistry and experimental biology","FirstCategoryId":"1085","ListUrlMain":"","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0
Abstract
The general kinetic parameters of IMP:NAD+ oxidoreductase, were investigated at 37 degrees C in normal human serum. These included substrate - velocity relationship, Km (IMP), Km (NAD), as well as the effect of temperature and pH on the kinetics of the reaction. Optimum conditions of IMP, NAD+ oxidoreductase in serum of normal Iraqi individuals at 37 degrees C were investigated. The optimum IMP concentration was found to be 0.6166 mM and the optimum NAD+ concentration was 6.28 mM, while the optimum pH for the reaction was found to be 8.3. The enzyme shows low stability even when the sera were incubated at low temperature. The activity of the enzyme is proportional to the serum concentration and its optimal temperature for the reaction was 37 degrees C. The enzyme was found to be inhibited by XMP, GMP competitively with Ki values of 0.0724 mM and 0.1583 mM respectively. The inhibition by thyroid hormone (T4) was studied giving a Ki value of 2.25 X 10(-6) mM. The mechanism of enzyme action was found to follow ordered sequential mechanism.
在37℃条件下，研究了正常人血清中IMP:NAD+氧化还原酶的一般动力学参数。其中包括底物-速度关系，Km (IMP)， Km (NAD)，以及温度和pH对反应动力学的影响。研究了37℃条件下伊拉克正常人血清中IMP、NAD+氧化还原酶的最佳条件。IMP的最佳浓度为0.6166 mM, NAD+的最佳浓度为6.28 mM，反应的最佳pH为8.3。即使血清在低温下孵育，酶也表现出低稳定性。酶的活性与血清浓度成正比，反应的最佳温度为37℃，XMP和GMP对酶有竞争性抑制作用，Ki值分别为0.0724 mM和0.1583 mM。在Ki值为2.25 X 10(-6) mM的条件下，研究了甲状腺激素(T4)的抑制作用，发现酶的作用机制遵循有序顺序机制。
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