Boag S, Jenkins C L
CSIRO, Division of Plant Industry, GPO Box 1600, Canberra A.C.T. 2601, Australia.
Plant Physiol. 1986 May;81(1):115-9. doi: 10.1104/pp.81.1.115.
Aspartate or glutamate stimulated the rate of light-dependent malate decarboxylation by isolated Zea mays bundle sheath chloroplasts. Stimulation involved a decrease in the apparent K(m) (malate) and an increased maximum velocity of decarboxylation. In the presence of glutamate other dicarboxylates (succinate, fumarate) competitively inhibited malate decarboxylation by intact chloroplasts with respect to malate with an apparent K(i) of about 6 millimolar. For comparison the K(i) for inhibition of nicotinamide adenine dinucleotide phosphate-malic enzyme from freshly lysed chloroplasts by these dicarboxylates was 15 millimolar. A range of compounds structurally related to aspartate stimulated malate decarboxylation by intact chloroplasts. K(a) values for stimulation at 5 millimolar malate were 1.7, 5, and 10 millimolar for l-glutamate, l-aspartate, and beta-methyl-dl-aspartate, respectively. Certain compounds, notably cysteic acid, which stimulated malate decarboxylation by intact chloroplasts inhibited malate decarboxylation by nicotinamide adenine dinucleotide phosphate-malic enzyme obtained from lysed chloroplasts and assayed under comparable conditions. It was concluded that aspartate, glutamate, and related compounds affect the transport of malate into the intact chloroplasts and that malate translocation does not take place on the general dicarboxylate translocator previously reported for higher plant chloroplasts.
天冬氨酸或谷氨酸可刺激离体玉米维管束鞘叶绿体中依赖光的苹果酸脱羧速率。这种刺激涉及表观K(m)（苹果酸）的降低和脱羧最大速度的增加。在谷氨酸存在的情况下，其他二羧酸（琥珀酸、富马酸）对完整叶绿体的苹果酸脱羧具有竞争性抑制作用，相对于苹果酸的表观K(i)约为6毫摩尔。相比之下，这些二羧酸对新鲜裂解叶绿体中烟酰胺腺嘌呤二核苷酸磷酸 - 苹果酸酶抑制作用的K(i)为15毫摩尔。一系列与天冬氨酸结构相关的化合物可刺激完整叶绿体的苹果酸脱羧。对于5毫摩尔苹果酸，l - 谷氨酸、l - 天冬氨酸和β - 甲基 - dl - 天冬氨酸刺激的K(a)值分别为1.7、5和10毫摩尔。某些化合物，特别是半胱氨酸，可刺激完整叶绿体的苹果酸脱羧，但能抑制在类似条件下测定的、从裂解叶绿体中获得的烟酰胺腺嘌呤二核苷酸磷酸 - 苹果酸酶的苹果酸脱羧。得出的结论是，天冬氨酸、谷氨酸及相关化合物影响苹果酸向完整叶绿体的转运，且苹果酸的转运并非通过先前报道的高等植物叶绿体的通用二羧酸转运体进行。
