Abstract
Aspartate kinase (EC 2.7.2.4.) has been purified from 7 day etiolated wheat (Triticum aestivum L. var. Maris Freeman) seedlings and from embryos imbibed for 8 h. The enzyme was 50% inhibited by 0.25 mM lysine. In this study wheat aspartate kinase was not inhibited by threonine alone or cooperatively with lysine; these results contrast with those published previously. In vivo regulation of the synthesis of aspartate-derived amino acids was examined by feeding [14C]acetate and [35S]sulphate to 2–3 day germinating wheat embryos in culture in the presence of exogenous amino acids. Lysine (1 mM) inhibited lysine synthesis by 86%. Threonine (1 mM) inhibited threonine synthesis by 79%. Lysine (1 mM) plus threonine (1 mM) inhibited threonine synthesis by 97%. Methionine synthesis was relatively unaffected by these amino acids, suggesting that there are important regulatory sites other than aspartate kinase and homoserine dehydrogenase. [35S]sulphate incorporation into methionine was inhibited 50% by lysine (2 mM) plus threonine (2 mM) correlating with the reported 50% inhibition of growth by these amino acids in this system. The synergistic inhibition of growth, methionine synthesis and threonine synthesis by lysine plus threonine is discussed in terms of lysine inhibition of aspartate kinase and threonine inhibition of homoserine dehydrogenase.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
Abbreviations
- AEC:
-
S-(2-aminoethyl) cysteine
References
Aarnes, H.: A lysine-sensitive aspartate kinase and two molecular forms of homoserine dehydrogenase from barley seedlings. Plant Sci. Lett. 9, 137–145 (1977)
Bright, S.W.J., Wood, E.A., Miflin, B.J.: The effect of aspartatede-rived amino acids (lysine, threonine, methionine) on the growth of excised embryos of wheat and barley. Planta 139, 113–117 (1978)
Bryan, J.K.: Studies on the catalytic and regulatory properties of homoserine dehydrogenase of Zea mays roots. Biochim. Biophys. Acta 171, 205–216 (1969)
Bryan, P.A., Cawley, R.D., Brunner, C., Bryan, J.K.: Isolation and characterization of a lysine-sensitive aspartate kinase from a multicellular plant. Biochem. Biophys. Res. Comm. 41, 1211–1217 (1970)
Cheshire, R.M., Miflin, B.J.: The control of lysine biosynthesis in maize. Phytochem. 14, 695–698 (1975)
Davies, H.M.: Regulation of amino acid biosynthesis in carrot tissue cultures. Ph.D. thesis, University of London U.K. (1977)
DiMarco, G., Grego, S.: Homoserine dehydrogenase in Pisum sativum and Ricinus communis. Phytochem. 14, 943–947 (1975)
Dodd, W.A., Cossins, E.A.: Biosynthesis of S-adenosylmethionine in germinating pea seeds. Phytochem. 7, 2143–2145 (1968)
Dunham, V.L., Bryan, J.K.: Synergistic effects of metabolically related amino acids on the growth of a multicellular plant. Plant Physiol. 44, 1601–1608 (1969)
Dunham, V.L., Bryan, J.K.: Synergistic effects of metabolically related amino acids on the growth of a multicellular plant II: Studies of 14C-amino acid incorporation. Plant Physiol. 47, 91–97 (1971)
Fricke, U.: Tritosol: A new scintillation cocktail based on Triton X-100. Anal. Biochem. 63, 555–558 (1975)
Green, C.E., Phillips, R.L.: Potential selection system for mutants with increased lysine, threonine, and methionine in cereal crops. Crop Sci. 14, 827–830 (1974)
Henke, R.R., Wilson, K.G., McClure, J.W., Treick, R.W.: Lysinemethionine-threonine interactions in growth and development of Mimulus cardinalis seedlings. Planta 116, 333–345 (1974)
Henke, R.R., Wilson, K.G.: In vivo evidence for metabolic control of amino acid and protein synthesis by exogenous lysine and threonine in Mimulus cardinalis. Planta 121, 155–166 (1974)
Johnston, F.B., Stern, H.: Mass isolation of viable wheat embryos. Nature 179, 160–161 (1957)
Lea, P.J., Fowden, L.: The purification and properties of glutamine-dependant asparagine synthetase isolated from Lupinus albus. Proc. Roy. Soc. Lond. B. 192, 13–25 (1975)
Lowry, O.H., Rosebrough, N.J., Farr, A.L., Randall, R.J.: Protein measurement with the Folin phenol reagent. J. Biol. Chem. 193, 265–275 (1951)
Madison, J.T., Thompson, J.F.: Threonine synthetase from higher plants: stimulation by S-adenosyl-methionine and inhibition by cysteine. Biochem. Biophys. Res. Comm. 71, 684–691 (1976)
Matthews, B.F., Gurman, A.W., Bryan, J.K.: Changes in enzyme regulation during growth of maize. I. Progressive desensitization of homoserine dehydrogenase during seedling growth. Plant Physiol. 55, 991–998 (1975)
Miflin, B.J.: Modification controls in time and space. In: Regulation of enzyme synthesis and activity in higher plants. pp. 23–39. Smith, H. ed. London: Academic Press 1977
Murashige, T., Skoog, F.: A revised medium for rapid growth and bioassays with tobacco tissue cultures. Physiol. Plant. 15, 473–497 (1962)
Oaks, A.: The effect of leucine on the biosynthesis of leucine in maize root tips. Plant Physiol. 40, 149–155 (1965)
Oaks, A., Bidwell, R.G.S.: Compartmentation of intermediary metabolites. Ann. Rev. Plant Physiol. 21, 43–66 (1970)
Shewry, P.R., Miflin, B.J.: Properties and regulation of aspartate kinase from barley seedlings (Hordeum vulgare L.). Plant Physiol. 59, 69–73 (1977)
Sloger, M., Owens, L.D.: Control of free methionine production in wild type and ethionine-resistant mutants of Chlorella sorokiniana. Plant Physiol. 53, 469–473 (1974)
Wong, K.F., Dennis, D.T.: Aspartokinase from wheat germ. Isolation, characterization and regulation. Plant Physiol. 51, 322–326 (1973a)
Wong, K.F., Dennis, D.T.: Aspartokinase in Lemna minor L. Studies on the in vivo and in vitro regulation of the enzyme. Plant Physiol. 51, 327–331 (1973b)
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Bright, S.W.J., Shewry, P.R. & Miflin, B.J. Aspartate kinase and the synthesis of aspartate-derived amino acids in wheat. Planta 139, 119–125 (1978). https://doi.org/10.1007/BF00387136
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00387136