Document Detail

Mechanisms of respiration and phosphorylation in Ascaris muscle mitochondria.
MedLine Citation:
PMID:  7442710     Owner:  NLM     Status:  MEDLINE    
In Ascaris muscle mitochondria the major respiratory chain-linked phosphorylation activity is accomplished by a NADH-linked reduction of fumarate to succinate. Oxygen can also be employed as a terminal electron acceptor via a cyanide- and salicyl-hydroxamate-resistant terminal oxidase. As in fumarate-dependent electron transport this process appears to be coupled to energy conservation at phosphorylation site I. The branchpoint from which electrons are taken from the main respiratory chain to either the alternative oxidase or fumarate reductase is likely to be on the oxygen side of the NADH dehydrogenase segment. Malate and succinate are the only substrates which appreciably support respiration in the mitochondrion of the nematode. Regardless of the presence or absence of oxygen malate is utilized by an oxidation-reduction reaction resulting in the formation of pyruvate, acetate, succinate, propionate and CO2. In addition, aerobically, hydrogen peroxide is formed as the product of oxygen reduction. Succinate accumulation was found to be significantly higher in the anaerobic as compared to the aerobic incubation mixtures. This effect was accompanied by an increase in anaerobic malate consumption. ATP generation and the formation of pyruvate, acetate and propionate were found to be similar in the presence and absence of oxygen. In malate-supported respiration of intact Ascaris mitochondria reducing equivalents (NADH) are produced exclusively through pyruvate and acetate formation. These enzymatic reactions are functionally coupled to the electron transport-linked reductions of fumarate to succinate and oxygen to hydrogen peroxide, respectively. In accordance with the position of the redox potentials of the fumarate/succinate and O2/H2O2 couples, anaerobic and aerobic respiration was found to be associated with relatively low energy conservation efficiencies. Thus one molecule of ATP was conserved per 2e- transferred to fumarate or oxygen, respectively. No evidence could be obtained for a significant activity of energy conservation sites II and III and electron transfer through the alternative oxidase pathway was shown not to be coupled to phosphorylation.
P Köhler; R Bachmann
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Molecular and biochemical parasitology     Volume:  1     ISSN:  0166-6851     ISO Abbreviation:  Mol. Biochem. Parasitol.     Publication Date:  1980 Apr 
Date Detail:
Created Date:  1981-02-24     Completed Date:  1981-02-24     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8006324     Medline TA:  Mol Biochem Parasitol     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  75-90     Citation Subset:  IM    
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MeSH Terms
Adenosine Triphosphate / metabolism
Ascaris / metabolism*,  ultrastructure
Electron Transport
Malates / metabolism*
Mitochondria, Muscle / metabolism*
Oxidoreductases / metabolism
Oxygen Consumption*
Succinate Dehydrogenase / metabolism
Succinates / metabolism*
Reg. No./Substance:
0/Malates; 0/Succinates; 56-65-5/Adenosine Triphosphate; EC 1.-/Oxidoreductases; EC Dehydrogenase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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