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Significance of the Enzymic Degradation of Cozymase in Living Organisms

Nature volume 163, pages 641–642 (1949)Cite this article

Abstract

REASON for the existence of a very potent enzyme system degrading cozymase in brain1 and in certain other cells and tissues2 has been obscure, as intact cozymase is so important to their normal functioning. The rate of breakdown by ground brain is of the order of 1 μmol./mgm. dry weight/hr.1, whereas the rate of respiration by the intact tissue is about 0·5 μmol./mgm. dry weight/hr. Brain preparations split the cozymase molecule between the pyridine-N and ribose1. The results in now show that the degrading enzyme can serve cellular economy in the following ways : (1) By decreasing the quantity of specifically the oxidized form of either coenzymes I or II in coenzyme-dihydrocoenzyme mixtures, their oxidation-reduction potentials can be expected to be lowered, and we have found this to be the case experimentally. (2) This can be expected to affect secondarily the many enzymes sensitive to changes in EH. (3) The degrading enzyme will compete with dehydrogenases for the oxidized forms of the coenzymes, and in mixtures of dehydrogenases favour the action of those of greatest affinity for the coenzymes. (4) Equilibria at certain dehydrogenases can be expected to be modified by the additional presence of an enzyme which removes one component from the system of four which are typically involved. Thus the formation of β-hydroxybutyric acid would be expected to be favoured in the β-hydroxybutyric–acetoacetate system.

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References

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  1. Research Laboratory, Maudsley Hospital, London, S.E.5

    H. MCILWAIN

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MCILWAIN, H. Significance of the Enzymic Degradation of Cozymase in Living Organisms. Nature 163, 641–642 (1949). https://doi.org/10.1038/163641a0

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