Schweizer P, Erismann K H
Pflanzenphysiologisches Institut, Altenbergrain 21, CH-3013 Bern, Switzerland.
Plant Physiol. 1985 Jul;78(3):455-8. doi: 10.1104/pp.78.3.455.
Young bean plants (Phaseolus vulgaris L. var Saxa) were fed with 3.5 or 10 millimolar N in either the form of NO(3) (-) or NH(4) (+), after being grown on N-free nutrient solution for 8 days. The pH of the nutrient solutions was either 6 or 4. The cell sap pH and the extractable activities of phosphoenolpyruvate carboxylase and of pyruvate kinase from roots and primary leaves were measured over several days.The extractable activity of phosphoenolpyruvate carboxylase (based on soluble protein) from primary leaves increased with NO(3) (-) nutrition, whereas with NH(4) (+) nutrition and on N-free nutrient solution the activity remained at a low level. Phosphoenopyruvate carboxylase activity from the roots of NH(4) (+)-fed plants at pH 4 was finally somewhat higher than from the roots of plants grown on NO(3) (-) at the same pH. There was no difference in activity from the root between the N treatments when pH in the nutrient solutions was 6. The extractable activity of pyruvate kinase from roots and primary leaves seemed not to be influenced by the N nutrition of the plants.The results are discussed in relation to the physiological function of both enzymes with special regard to the postulated functions of phosphoenolpyruvate carboxylase in C3 plants as an anaplerotic enzyme and as part of a cellular pH stat.
将嫩菜豆植株（菜豆品种Saxa）在无氮营养液中培养8天后，分别以3.5或10毫摩尔的硝酸根（NO₃⁻）或铵根（NH₄⁺）形式供给氮素。营养液的pH值为6或4。在几天内测定了根和初生叶的细胞液pH值以及磷酸烯醇式丙酮酸羧化酶和丙酮酸激酶的可提取活性。初生叶中磷酸烯醇式丙酮酸羧化酶（基于可溶性蛋白）的可提取活性随硝酸根（NO₃⁻）营养而增加，而在铵根（NH₄⁺）营养和无氮营养液条件下，该活性维持在较低水平。在pH值为4时，铵根（NH₄⁺）处理植株根中的磷酸烯醇式丙酮酸羧化酶活性最终略高于相同pH值下硝酸根（NO₃⁻）处理植株的根。当营养液pH值为6时，氮处理间根中的活性没有差异。根和初生叶中丙酮酸激酶的可提取活性似乎不受植株氮营养的影响。结合这两种酶的生理功能，特别是关于磷酸烯醇式丙酮酸羧化酶在C3植物中作为回补酶和细胞pH稳态一部分的假定功能，对结果进行了讨论。
