Direct oxidases

Butt VS (1980) Direct oxidases and related enzymes. In Davies R (ed) The biochemistry of plants. A comprehensive treatise. Metabolism and respiration 2. Academic Press, New York, p 85... 

Peroxidase can be activated by a thermostable factor in pea seedlings to be a direct oxidase toward phenylacetaldehyde (413). Purified horse-radish peroxidase plus manganous ions behaves similarly toward this substrate. In either case, benzaldehyde and formic acid are the primary products, but the oxygen stoichiometry of the reaction is obscured by side reactions. Catalase has an inhibiting effect, which suggests that peroxide is an obligatory intermediate or activator. 

Manganous ions activate peroxidase as an oxidase toward oxalate, oxalacetate, ketomalonate, and dihydroxytartrate. A peroxidase substrate is necessary for the reaction with the first two substrates, but not for the last two. These reactions depend upon the presence of peroxide. They can be facilitated by adding peroxide, or inhibited by adding catalase, but it is uncertain whether they are instances of direct oxidase action, or of peroxidatic activity (414). 

Dyer R B, Einarsdottir 6, Killough P M, Lopez-Garriga J J and Woodruff W H 1989 Transient binding of photodissociated CO to of eukaryotic cytochrome oxidase at ambient temperature. Direct evidence from time-resolved infrared spectroscopy J. Am. Chem. Soc. Ill 7657-9... 

Entrapment of biochemically reactive molecules into conductive polymer substrates is being used to develop electrochemical biosensors (212). This has proven especially useful for the incorporation of enzymes that retain their specific chemical reactivity. Electropolymerization of pyrrole in an aqueous solution containing glucose oxidase (GO) leads to a polypyrrole in which the GO enzyme is co-deposited with the polymer. These polymer-entrapped GO electrodes have been used as glucose sensors. A direct relationship is seen between the electrode response and the glucose concentration in the solution which was analyzed with a typical measurement taking between 20 to 40 s. 

Methoxatin, now known as coenzyme PQQ, was originally obtained from methylotrophic bacteria but is now known to be a mammalian cofactor, for example, for lysyl oxidase and dopamine p-hydroxylase. The first synthesis of this rare compound was accomplished by the route outlined below. In the retrosynthetic analysis both of the heterocyclic rings were disconnected using directly keyed transforms. 

Garrett, R. M., and Rajagopalan, K V., 1996. Site-directed mutagenesis of recombinant snlfite oxidase. Journal of Biological Chemistry 271 7387-7391. 

Complex rV is called, cytochrome c oxidase because it accepts electrons from cytochrome c and directs them to the four-electron reduction of O2 to form H2O ... 

At the present time, the greatest importance of covalent hydration in biology seems to lie in the direction of understanding the action of enzymes. In this connection, the enzyme known as xanthine oxidase has been extensively investigated.This enzyme catalyzes the oxidation of aldehydes to acids, purines to hydroxypurines, and pteridines to hydroxypteridines. The only structural feature which these three substituents have in common is a secondary alcoholic group present in the covalently hydrated forms. Therefore it was logical to conceive of this group as the point of attack by the enzyme. 

Since it might be possible that the perturbation of membrane directly stimulated the NADPH-oxidase located on the cell membrane, which is the enzyme for the production of superoxide [24], the possibility was examined by the assay using detergent (Triton X-100) instead of polymers. At 0.001% of Triton X-100, no stimulation of superoxide release from DMSO-differentiated HL-60 cells was observed. At 0.01% of Triton X-100, a... 

False. D-gluconolactone is produced directly from glucose via glucose oxidase. 6-phosphogluconolactone is an intermediate in the hexose monophosphate pathway. 

MDMA overdose as well as the concomitant consumption of selective serotonin reuptake inhibitors (SSRI) with other dmgs that exert serotoninergic effects (such as inhibitors of monoamine oxidase) can rapidly lead to the serotonin syndrome. Its symptoms, which are reversible upon cessation, of the drug include confusion, muscle rigidity in the lower limbs, and hyperthermia suggesting an acute reaction to serotonin overflow in the CNS. Blocking the function of SERT outside the brain causes side effects (e.g., nausea), which may be due to elevated 5HT however , impairment of transporter function is not equivalent to direct activation of 5HT recqrtors in causing adverse effects such as fibrosis and pulmonary hypertension. 

Further improvements can be achieved by replacing the oxygen with a non-physiological (synthetic) electron acceptor, which is able to shuttle electrons from the flavin redox center of the enzyme to the surface of the working electrode. Glucose oxidase (and other oxidoreductase enzymes) do not directly transfer electrons to conventional electrodes because their redox center is surroimded by a thick protein layer. This insulating shell introduces a spatial separation of the electron donor-acceptor pair, and hence an intrinsic barrier to direct electron transfer, in accordance with the distance dependence of the electron transfer rate (11) ... 

Upon mutagenesis of the monoamine oxidase from Aspergillus niger (MAO-N) within several rounds of directed evolution [65], variant biocatalysts were identified with largely expanded substrate acceptance, enabling also the deracemization of tertiary amines incorporating straight-chain and cyclic structural motifs [66]. 

Glucuronate is reduced to L-gulonate in an NADPH-dependent reaction L-gulonate is the direct precursor of ascorbate in those animals capable of synthesizing this vitamin. In humans and other primates as well as guinea pigs, ascorbic acid cannot be synthesized because of the absence of L-g ulonolactone oxidase. L-Gulonate is metabolized ultimately to D-xylulose 5-phosphate, a constituent of the pentose phosphate pathway. 

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