Enzymes Oxidation with

Bischler-Napieralski and Pictet Spengler reactions continue to serve well for benzylisoquinoline syntheses.76,77 In the latter reaction, use of a-formylphenyl-acetic esters for the non-nitrogen-containing component appears to be advantageous.77 An interesting sequence of reactions (43)—>—>(44) (Scheme 4) has apparently been applied to the synthesis of papaverine [44 R = 3,4-(MeO)2-C6H3CH2 ] and related alkaloids.78 An attempt to convert ( )-reticuline (37 R = H) into a morphinandienone-type alkaloid by enzymic oxidation with... 

A -Pyrroline has been prepared in low yield by oxidation of proline with sodium hypochlorite (71), persulfate (102), and periodate (103). A -Pyrroline and A -piperideine are products of enzymic oxidation via deamination of putrescine and cadaverine or ornithine and lysine, respectively (104,105). This process plays an important part in metabolism and in the biosynthesis of various heterocyclic compounds, especially of alkaloids. 

All prostaglandins are cyclopentanoic acids derived from arachidonic acid. The biosynthesis of prostaglandins is initiated by an enzyme associated with the endoplasmic reticulum, called prostaglandin endoperoxide synthase, also known as cyclooxygenase. The enzyme catalyzes simultaneous oxidation and cyclization of arachidonic acid. The enzyme is viewed as having two distinct activities, cyclooxygenase and peroxidase, as shown in Figure 25.28. 

Other examples are the use of osmium(VIII) oxide (osmium tetroxide) as catalyst in the titration of solutions of arsenic(III) oxide with cerium(IV) sulphate solution, and the use of molybdate(VI) ions to catalyse the formation of iodine by the reaction of iodide ions with hydrogen peroxide. Certain reactions of various organic compounds are catalysed by several naturally occurring proteins known as enzymes. 

Ribosomal protein L12 was oxidized with N-chlorosuccinimide as described by Schechter and coworkers28 and dialyzed. The complete system contained 33 mM Tris-HCI (pH 7.4), 13mM MgCI2,275 pmol Met(0)-L12,13mM dithiothreitol (or 2-mercaptoethanol where indicated), and enzyme. See the legend to Figure 5 for further details of the assay. 

One 7i-bond of an aromatic ring can be converted to a cyclohexadiene 1,2-diol by reaction with enzymes associated with P. putida A variety of substituted aromatic compounds can be oxidized, including bromobenzene, chlorobenzene, " and toluene. In these latter cases, introduction of the hydroxyl groups generates a chiral molecule that can be used as a template for asymmetric syntheses. " ... 

The cysteinyl residue in the core was oxidized with performic acid according to the method of Hirs ( ) and the oxidized core was digested with chymotrypsin for 8 hours at room temperature in a pH stat at pH 8.9. Enzyme equal to 0.5% of the substrate by weight was added at 0 and at 2 hr. The chymotryptic peptides were also separated by Dowex 50-X4 chromatography. 

Chemical modifications like alkylation with (A-ethylmaleimide (NEM) or oxidation with diamide that inhibit the phosphorylation activity of the enzyme did not seem to have any significant effect on the high affinity binding site when the enzyme was solubilized in the detergent decyl-PEG [69,41]. However, in the intact membrane these treatments reduced the affinity by a factor of 2-3. The reduction of the affinity was exclusively due to modification of the cysteine residue at position 384 in the B domain [69]. Apparently, the detergent effects the interaction between the B and C domains. 

Armstrong, D.A. and Buchanan, J.D. (1978). Reactions of O2, H2O2 and other oxidants with sulfhydryl enzymes. Photochem. Photobiol. 28, 743-755. 

Important inherent characteristics of an enzyme that should be considered are the substrate affinity, characterized by the Michaelis constant the rate of turnover fecat> providing the catalytic efficiency fecat/ M. and the catalytic potential. Several attempts to compare enzyme catalysis with that of platinum have been published. Direct comparisons are difficult, because enzyme electrodes must be operated in aqueous electrolyte containing dissolved substrate, whereas precious metal electrodes aie often supplied with a humidified gaseous stream of fuel or oxidant, and produce water as steam. It is not straightforward to compare tme optimal turnover rates per active site, as it is often unclear how many active sites are being engaged in a film of enzyme on an electrode. 

The initial electrochemical and biological oxidation with xanthine oxidase are essentially identical. However, electrochemically 2,8-dioxyadenine the final product in the presence of xanthine oxidase is much more readily oxidizable than adenine 59) so that considerable further oxidation occurs. To the authors knowledge, 2,8-dioxyadenine is not a major metabolite of adenine in man or other higher organisms. Accordingly, it is likely that other enzymes accomplish further degradation of 2,8-dioxyadenine. The relationship between the products so formed and the mechanism of the reaction to the related electrochemical processes has yet to be studied. 

Adam, W., Lazarus, M., Boss, B. et al. (1997) Enzymic resolution of chiral 2-hydroxy carboxylic acids by enantioselective oxidation with molecular oxygen catalyzed by the glycolate oxidase from spinach (Spinacia oleracea). The Journal of Organic Chemistry, 62 (22), 7841-7843. 

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