| Popis: |
Publisher Summary This chapter presents the enzymic free radical mechanisms of various enzymes, such as ribonucleotide reductases, monoamine oxidase, DNA photolyase, and pyruvate formate-lyase. In the chapter, a general mechanistic scheme for RDPR and RTPR catalysis is shown. The experimental results for the verification of this mechanism are discussed. These strategies have involved elegant isotope effect and stereochemical studies with the usual nucleoside di- and triphosphates. The enzymic processing of alternate substrates modified in the 2′-position has led to the discovery of new mechanism-based inhibitors, whose mechanism of inactivation is consistent with the hypothesis for substrate processing described in the chapter. The mechanisms of ribonucleotide-diphosphate reductases (RDPR) and ribonucleoside-5′-triphosphate reductases (RTPR) are similar despite the difference in the cofactors for the respective reactions—that is, tyrosyl radical and AdoCbl. Finally, the evidence, or the lack of evidence, for the direct involvement of the enzyme radical species in the catalytic cycle is discussed. |
