Oxidation reactions enzymes

Oxidation is the second major process in degradation of cocaine, and it occurs in the liver as a result of activity of microsomal cytochrome P-450 enzymes. Oxidative reactions account for hydroxylation of the aromatic ring of the benzoic acid moiety and for N-demethylation [30, 42, 43]. Specifically, it appears to be the 3a form of P-450 that is responsible, since feeding inhibitors of this isoform to mice inhibited the hepatotoxicity caused by the demethylated product [44],... 

It has been suggested that biological oxidation-reduction reactions occur by way of one electron transfer As a consequence of univalent transfer of electrons in the oxidation of organic molecules free radicals are produced at the end of the first step. With the help of electron paramagnetic resonance spectrometer it has been established that several enzymic oxidation reactions involve one-electron transfer processes. 

Phenolic compounds are commonplace natural products Figure 24 2 presents a sampling of some naturally occurring phenols Phenolic natural products can arise by a number of different biosynthetic pathways In animals aromatic rings are hydroxylated by way of arene oxide intermediates formed by the enzyme catalyzed reaction between an aromatic ring and molecular oxygen... 

Oxidative Reactions. The majority of pesticides, or pesticide products, are susceptible to some form of attack by oxidative enzymes. For more persistent pesticides, oxidation is frequently the primary mode of metaboHsm, although there are important exceptions, eg, DDT. For less persistent pesticides, oxidation may play a relatively minor role, or be the first reaction ia a metaboHc pathway. Oxidation generally results ia degradation of the parent molecule. However, attack by certain oxidative enzymes (phenol oxidases) can result ia the condensation or polymerization of the parent molecules this phenomenon is referred to as oxidative coupling (16). Examples of some important oxidative reactions are ether cleavage, alkyl-hydroxylation, aryl-hydroxylation, AJ-dealkylation, and sulfoxidation. 

Chemiluminescent labels, in which the luminescence is generated by a chemical oxidation step, and bioluminescent labels, where the energy for light emission is produced by an enzyme-substrate reaction, are additional labeling types (39,42). Luminol [521 -31 -3] CgHyN202, and acridine [260-94-6] C H N, derivatives are often used as chemiluminescent labels. 

Oxidative substitutions at ring junction positions in various tetrahydro-5-deaza-pterins (79JA6068) and -flavins (77JA6721) have been studied, e.g. to give (13), and the oxidation-reduction reactions of 5-deazaflavins (e.g. 78CL1177, 80CPB3514) across the 1,5-positions, e.g. (19) (20), are involved in their co-enzymic role in enzymic oxidations (see Section... 

FIGURE 24.10 The /3-oxidation of saturated fatty acids involves a cycle of fonr enzyme-catalyzed reactions. Each cycle produces single molecnles of FADH, NADH, and acetyl-CoA and yields a fatty acid shortened by two carbons. (The delta [A] symbol connotes a double bond, and its superscript indicates the lower-nnmbered carbon involved.)... 

The third reaction of this cycle is the oxidation of the hydroxyl group at the /3-position to produce a /3-ketoacyl-CoA derivative. This second oxidation reaction is catalyzed by L-hydroxyacyl-CoA dehydrogenase, an enzyme that requires NAD as a coenzyme. NADH produced in this reaction represents metabolic energy. Each NADH produced in mitochondria by this reaction drives the synthesis of 2.5 molecules of ATP in the electron transport pathway. L-Hydroxyacyl-... 

The tripeptide LLD-ACV is then cydised to isopenicillin N by an oxidative reaction involving the removal of four protons. The enzyme that catalyses this reaction is isopenidllin N synthetase or synthase (IPNS). 

Enzyme-mediated oxidation reactions offer highly diverse options for the modification of existing functional groups as well as for the introduction of novel function in chiral catalysis. Biooxidations often enable us to obtain complementary solutions to metal-assisted transformations and organocatalysis and are considered one of the important strategies of green chemistry . 

Table 16-7 The surface or enzyme-catalyzed reaction rate constant, Mn/ for oxidation of Mn normalized for oxygen concentration [O2], pH and particulate concentration [X]. d[Mn ]/dt = Mn [Mn][02][0H] [X]...

Oxidation is initiated by formation of radicals which may be the result of enzyme catalysed reactions like oxygen activation by xanthine oxidase in... 

One-step hydroxylation of aromatic nucleus with nitrous oxide (N2O) is among recently discovered organic reactions. A high eflSciency of FeZSM-5 zeolites in this reaction relates to a pronounced biomimetic-type activity of iron complexes stabilized in ZSM-5 matrix. N2O decomposition on these complexes produces particular atomic oj gen form (a-oxygen), whose chemistry is similar to that performed by the active oxygen of enzyme monooxygenases. Room temperature oxidation reactions of a-oxygen as well as the data on the kinetic isotope effect and Moessbauer spectroscopy show FeZSM-5 zeolite to be a successfiil biomimetic model. 

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