Oxidation via activation

In addition to influencing the rate of lipid oxidation via activation of thiol groups and metallo-enzymes, heating milk may also affect oxidation via redistribution of Cu (which migrates to the FGM on heating) and possibly by the formation of Maillard browning products, some of which have metal chelating and antioxidant properties. 

Schaefer U, Schneider A, Rixen D, Neugebauer E (1998) Neutrophil adhesion to histamine stimulated cultured endothelial cells is primarily mediated via activation of phospholipase C and nitric oxide synthase isozymes. Inflamm Res 47(6) 256-264 Schaefer U, Schmitz V, Schneider A, Neugebauer E (1999) Histamine induced homologous and heterologous regulation of histamine receptor subtype mRNA expression in cultured endothelial ceUs. Shock 12(4) 309-315... 

These reactions demonstrate the Brflnsted base role of adsorbed oxygen perviously found on Ag(llO) and show further that more active transition metals which themselves activate C-H bonds catalytically oxidize via a two-step mechanism in which the surface intermediates are scavenged by adsorbed oxygen. 

Alkane oxidation via a hydroperoxide was suggested many years ago, and seems to be operative in Acinetobacter sp. strain M-1 that has, in addition, a rather unusual range of substrates that include both n-alkanes and -alkenes. The purified enzyme contains FAD and requires copper for activity (Maeng et al. 1996). 

Marker, H.S., Weiss, C., Silides, D.J., and Cohen, G. (1981). Coupling of dopamine oxidation (monoamine oxidase activity) to glutathione oxidation via the generation of hydrogen peroxide in rat brain homogenates. J. Neurochem. 36, 589-593. 

Adenine phosphoribosyltransferase (APRT) deficiency is an inherited disorder of purine metabolism and is inherited in an autosomal recessive manner (K18, V7). This enzyme deficiency results in an inability to salvage the purine base adenine, which is oxidized via the 8-hydroxy intermediate by xanthine oxidase to 2,8-di-hydroxyadenine (2,8-DHA). This produces crystalluria and the possible formation of kidney stones due to the excretion of excessive amounts of this insoluble purine. Type I, with virtually undetectable enzyme activity, found predominantly in Caucasians, is found in homozygotes or compound heterozygotes for null alleles. Type II, with significant APRT activity, found only in Japan, is related to a missense mu-... 

Chain propagation proceeds in ester oxidation via the reaction of the ester peroxyl radical with weakest C—H bond of the ester. Is the activity of the ester peroxyl radical same as alkyl peroxyl radical Let us compare the rate constants of two different peroxyl radicals reactions with the same ester group, namely, RCH2C(0)0CH2R. 

Auge, N., Nikolova-Karakashian, M., Carpentier, S., Parthasarathy, S., Negre-Salvayre, A., Salvayre, R., Merrill, A.H. Jr, Levade, T, 1999, Role of sphingosine 1-phosphate in the mitogenesis induced by oxidized LDL in smooth muscle cells via activation of sphingomyelinase, ceramidase, and sphingosine kinase, J. Biol. Chem. 274 21533-21538. 

To elucidate the metabolic pathway of phenylmalonic acid, the incubation broth of A. bronchisepticus on phenylmalonic acid was examined at the early stage of cultivation. After a one-day incubation period, phenylmalonic acid was recovered in 80% yield. It is worthy of note that the supposed intermediate, mandelic acid, was obtained in 1.4% yield, as shown in Eq. (8). The absolute configuration of this oxidation product was revealed to be S. After 2 days, no metabolite was recovered from the broth. It is highly probable that the intermediary mandelic acid is further oxidized via benzoylformic acid. As the isolated mandelic acid is optically active, the enzyme responsible for the oxidation of the acid is assumed to be S-specific. If this assumption is correct, the enzyme should leave the intact l -enantiomer behind when a racemic mixture of mandelic acid is subjected to the reaction. This expectation was nicely realized by adding the racemate of mandelic acid to a suspension of A. bronchisepticus after a 4-day incubation [4]. 

Two conditions in which the rate of ketone body formation is increased are hypoglycaemia and prolonged starvation in adults or short-term starvation in children. What is the mechanism for increasing the rate Although there are several fates for fatty acids in the liver, triacylglycerol, phospholipid and cholesterol formation and oxidation via the Krebs cycle, the dominant pathway is ketone body formation (Figure 7.20). Three factor regulate the rate of ketone body formation (i) hormone sensitive lipase activ-... 

Figure 19.17 The biochemistiy and physiology responsible for penile erection. Sexual activity itself begins with a state of arousal that leads to erection. Arousal results in part from stimulation of the sense organs. The hypothalamus coordinates the sensations and activates the autonomic nervous system. Sensory nerves from the skin of the penis and other erogenous zones stimulate the parasympathetic system. This activates nitric oxide synthase and the resultant nitric oxide, via cyclic GMP, causes vasodilation of the arterioles. This increases blood flow through the corpora cavernosa which then expands producing an erection. Pheromones secreted by the female can stimulate the odour detecting system in the nasal cavity of the male (Chapter 12 and see above). Stress, however, activates the sympathetic system releases cyclic AMP which can result in vasoconstriction of the arterioles. Other factors that can interfere with an erection are physical fatigue and alcohol.

Ince NFI, Apikyan IG (2000) Combination of activated carbon adsorption with light-enhanced chemical oxidation via hydrogen peroxide. Water Res 34 4169 176... 

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