Abstract
Rates of synthesis and turnover of nitrate reductase in Chlorella vulgaris have been estimated from density-labelling experiments. It is demonstrated that nitrate stimulates the rate of turnover of the enzyme. Upon transfer of Chlorella from ammonium to nitrate medium there is a rapid increase in nitrate reductase activity, only part of which is a consequence of increased de novo synthesis: there must also be considerable activation of existing enzyme. It is shown that, in the absence of nitrate, the enzyme is very stable in vivo. Upon transfer from nitrate to ammonium medium, synthesis of nitrate reductase is reduced below the limits of defection. These effects are separate from the reversible (ferricyanide-reactivatable) inactivation of the enzyme which is also observed.
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Abbreviations
- Kat:
-
Katal (One katal is defined as the amount of enzyme which will catalyse the formation of 1 mol of NO-2 s-1 at 25°C)
References
Hewitt, E.J.: Assimilatory nitrate-nitrite reduction. Annu. Rev. Plant Physiol. 26, 73–100 (1975)
Johnson, C.B., Attridge, T.H., Smith, H.: Advantages of the fixedangle rotor for the separation of density-labelled from unlanelled proteins by isopycnic equilibrium centrifugation. Biochim. Biophys. Acta 317, 219–230 (1973)
Losada, M., Paneque, A., Aparicio, P.J., Vega, J.M., Cardenas, J., Herrera, J.: Inactivation and repression by ammonium of the nitrate reducing system in Chlorella. Biochem. Biophys. Res. Commun. 38, 1009–1010 (1970)
Pistorius, E.K., Gewitz, H-S., Voss, H., Vennesland, B.: Reversible inactivation of nitrate reductase in Chlorella vulgaris in vivo Planta 128, 73–80 (1976)
Solomonson, L.P., Jetschmann, K., Vennesland, B.: Reversible inactivation of the nitrate reductase of Chlorella vulgaris Beijerinck. Biochim. Biophys. Acta 309, 32–43 (1973)
Stewart, G.R., Rhodes, D.: Control of enzyme levels in the regulation of nitrogen assimilation. In: Regulation of enzyme synthesis and activity in higher plants. pp. 1–22, Smith, H., ed. London, New York, San Francisco: Academic Press
Tischner, R., Hüttermann, A.: Light-mediated activation of nitrate reductase in synchronous Chlorella. Plant Physiol. 62, 284–286 (1978)
Vennesland, B., Jetschmann, C.: The nitrate reductase of Chlorella vulgaris. Biochim. Biophys. Acta 227, 554–564 (1971)
Zielke, H.R., Filner, P.: Synthesis and turnover of nitrate reductase induced by nitrate in cultured tobacco cells. J. Biol. Chem. 246, 1772–1779 (1971)
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Johnson, C.B. Activation, synthesis and turnover of nitrate reductase controlled by nitrate and ammonium in Chlorella vulgaris . Planta 147, 63–68 (1979). https://doi.org/10.1007/BF00384592
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DOI: https://doi.org/10.1007/BF00384592