Animal Life Without Oxygen: Basic Biochemical Mechanisms

It is among these groups that we find the true facultative anaerobes, capable of utilizing O2 if it is present, and quite capable of indefinite survival in its absence

PETER W. HOCHACHKA; JEREMY FIELDS; TARIQ MUSTAFA

2007

Scholarcy highlights

  • In all cells that are able to sustain significant periods of anoxia some provision is made for a storage form of energy to be utilized during anoxia, the maintenance of redox balance, and the generation of high energy phosphate compounds. In many organisms these basic metabolic requirements are met by anaerobic glycolysis where glycogen, the storage form of energy, is metabolized to the level of lactate during anaerobiosis
  • Redox balance is maintained by a functionally 1:1 organization of GAPDH* and LDH: The NAD utilized in the GAPDH oxidation is regained by LDH catalyzed reduction of pyruvate to lactate, and the scheme as regards NAD is cyclic and catalytic
  • As a rough "thumb-nail sketch," species with highly developed anaerobic capacities are to be found among the nematodes, trematodes, cestodes, annelids, molluscs and probably some arthropods. It is among these groups that we find the true facultative anaerobes, capable of utilizing O2 if it is present, and quite capable of indefinite survival in its absence
  • Recent studies by Isserhoff et al convincingly demonstrate that proline is one of the chief metabolites released by Fasciola into its environment; that is, in this organism at least, proline occurs in high titre not because it is a potential substrate but rather because it is an important end product of energy metabolism
  • A third kind of ATP-generating reaction process "harnessed" by facultative anaerobes appears to involve a step in the electron transfer system: that involving the reduction of fumarate to succinate
  • All of these results would be anticipated if the classical glycolytic production of ATP were being supplanted by fumarate reduction coupled to the electron transfer system, by glutamate mobilization through the a-KGA -> succinylCoA -> succinate pathway, or by both mechanisms in a manner directly comparable to that of invertebrate facultative anaerobes

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