Burnell J N, Hatch M D
Division of Plant Industry, CSIRO, Canberra, Australia.
Arch Biochem Biophys. 1988 Jan;260(1):177-86. doi: 10.1016/0003-9861(88)90439-0.
A method has been developed for rapidly preparing bundle sheath cell strands from Urochloa panicoides, a phosphoenolpyruvate (PEP) carboxykinase-type C4 plant. These cells catalyzed both HCO3(-)- and oxaloacetate-dependent oxygen evolution; oxaloacetate-dependent oxygen evolution was stimulated by ATP. For this activity oxaloacetate could be replaced by aspartate plus 2-oxoglutarate. Both oxaloacetate- and aspartate plus 2-oxoglutarate-dependent oxygen evolution were accompanied by PEP production and both were inhibited by 3-mercaptopicolinic acid, an inhibitor of PEP carboxykinase. The ATP requirement for oxaloacetate- and aspartate plus 2-oxoglutarate-dependent oxygen evolution could be replaced by ADP plus malate. The increased oxygen evolution observed when malate plus ADP was added with oxaloacetate was accompanied by pyruvate production. These results are consistent with oxaloacetate being decarboxylated via PEP carboxykinase. We suggest that the ATP required for oxaloacetate decarboxylation via PEP carboxykinase may be derived by phosphorylation coupled to malate oxidation in mitochondria. These bundle sheath cells apparently contain diffusion paths for the rapid transfer of compounds as large as adenine nucleotides.
已开发出一种从狼尾草（一种磷酸烯醇式丙酮酸羧激酶型C4植物）快速制备维管束鞘细胞束的方法。这些细胞催化了依赖于HCO3(-)和草酰乙酸的放氧反应；依赖于草酰乙酸的放氧反应受到ATP的刺激。对于这种活性，草酰乙酸可以被天冬氨酸加2-氧代戊二酸替代。依赖于草酰乙酸和天冬氨酸加2-氧代戊二酸的放氧反应都伴随着磷酸烯醇式丙酮酸（PEP）的产生，并且两者都受到PEP羧激酶抑制剂3-巯基吡啶甲酸的抑制。依赖于草酰乙酸和天冬氨酸加2-氧代戊二酸的放氧反应对ATP的需求可以被ADP加苹果酸替代。当苹果酸加ADP与草酰乙酸一起添加时观察到的放氧增加伴随着丙酮酸的产生。这些结果与草酰乙酸通过PEP羧激酶脱羧一致。我们认为，通过PEP羧激酶使草酰乙酸脱羧所需的ATP可能通过与线粒体中苹果酸氧化偶联的磷酸化作用产生。这些维管束鞘细胞显然含有用于快速转移像腺嘌呤核苷酸这样大分子化合物的扩散途径。
