Alternative respiratory pathway

Maturation effected the following changes In enzymes and metabolites in orange fruit ethanol and acetaldehyde accumulated to levels of 10 mM and 0.08 mM, pyruvate decreased about 30%, pyruvate decarboxylase increased over 4 fold, alcohol dehydrogenase increased about 2 fold, the NADH to NAD ratio increased 21/2 fold and the terminal oxidase developed CN-insensitivity. The fraction of the total alternative respiratory pathway in actual use increased from 0.46 to 1.08. Induction of the alternative, CN-insensitive oxidase during maturation was interpreted as indicating that membrane function was modified which affected metabolic pathways resulting in the accumulation of ethanol and acetaldehyde. 

Induction of the alternative respiratory pathway has been observed in maturing and aging organs, tissues and cells (22). 

Karaffa L, Sandor E, Kozma J, Kubicek CP, Szentirmai A. The role of the alternative respiratory pathway in the stimulation of cephalosporin C formation by soybean oil in Acremonium chrysogenum. Appl Microbiol Biotechnol 51 (5) 633 —638, 1999. 

I. Thus when electrons enter the alternative respiratory pathway through the rotenone-insensitive NADH dehydrogenase, the external NADH dehydrogenase, or succinate dehydrogenase (Complex II), and pass to O2 via the cyanide-resistant alternative oxidase, energy is not conserved as ATP but is released as heat. A skunk cabbage can use the heat to melt snow, produce a foul stench, or attract beetles or flies. 

Unden G, Bongaerts J. Alternative respiratory pathways of Escherichia coli energetics and transcriptional regulation in response to electron acceptors. Biochim Biophys Acta 1997 1320 217-234. 

Three explanations had been proposed. (8)a) The equations proposed by Groen et. al.( 4 ) using specific inhibitors may overestimate the Ci, b) some reactions could be draining the main flux (alternative respiratory pathway) and c) partial channeling of some intermediate metabolites. 

Siedow, J. N. and Girvin, M. E. (1980). Alternative respiratory pathway its role in seed respiration and its inhibition by propyl gallate. Plant Physiol. 65, 669-674. 

KIRIMURA, K., YODA, M., SHIMIZU, H., SUGANO, S., MIZUNO, M., KINO, K., USAMI, S., Contribution of cyanide-insensitive respiratory pathway, catalyzed by the alternative oxidase, to citric acid production in Aspergillus niger, Biosci. Blotechnol. Blochem., 2000, 64, 2034-2039. 

One study has reported that aqueous extracts of the neem leaf produced anti-complement activity specifically in the classic pathway, but no stimulation of PMN phagocytosis or respiratory burst as measured by nitroblue tetrazoleum reduction [8]. Two polymers are believed to be responsible for the anti-complement activity of Azadharichta indica [69]. Further, the aqueous extract of the bark also reduced both classical and alternative complement pathway activity [70]. The effect was found to be dose and time dependent and most pronounced in the classical pathway. 

Thus although the operation of the pentose phosphate pathway alone or in conjunction with the TCA cycle can cause the complete dissimilation of glucose to CO it is certain that this pathway is more than simply an alternative respiratory route. The evidence suggests that it is deeply involved in the utilisation of carbohydrates to generate reduced coenzymes and intermediates destined for synthetic reactions. 

Cyanide has many sources natural (plant-Cassava), industrial (cyanide salts and nitriles), and accidental (fires). The target organ is the brain death is from respiratory arrest. Cyanide blocks cytochrome a-a3 (cytochrome oxidase) in mitochondria. The toxic level is 1 mg mL-1 in blood. Treatment involves giving dicobalt edetate (chelation). Alternatively, by giving NaNCb, levels of methemoglobin are increased, and this binds cyanide. Detoxication is catalyzed by the enzyme rhodanese, and this pathway may be increased by giving NaS207. 

The respiratory systems of bacteria are of especial interest1435 and complexity in view of their ability in some cases to use alternative substrates as terminal electron acceptors, depending upon the environmental conditions. This will be illustrated with reference to E. coli, which has been reviewed recently.1436 The advantage of studying respiration in this organism is that, by choice of growth conditions, the pathways of electron transport can be manipulated. In addition, mutants are available which are defective in certain respiratory components. 

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