Luo C, Kleczkowski L A
Department of Plant Physiology, Umeå University, Sweden.
Phytochemistry. 1999 Jan;50(2):209-14. doi: 10.1016/s0031-9422(98)00472-5.
Full length cDNAs for barley ADP-glucose pyrophosphorylase (AGPase) coding for the large subunits of the endosperm and leaf homologues of the enzyme (AGPase-S1 and -S2, respectively) and for the small subunit protein from endosperm (AGPase-B1), have been expressed in Escherichia coli. The cDNAs for AGPase-S1 and -S2 required different induction conditions for their maximal expression and they encoded immunologically distinct proteins. The AGPase-S1 that was produced by E. coli had the same M(r) (58 kDa) as the corresponding protein in barley crude endosperm extracts, whereas the bacteria-produced AGPase-S2 (55 kDa) was larger than its counterpart from barley leaf preparations (53 kDa). An enzymatically active AGPase expressed in E. coli from a double construct containing cDNAs for AGPase-S1 and -B1 subunits was insensitive to the activation by 3-phosphoglycerate and to inhibition by inorganic phosphate, similarly to the enzyme in barley endosperm. Neither AGPase-S1 nor -B1 were active when expressed alone in the bacteria. The data are discussed with respect to possible mechanisms of intracellular targeting of immature AGPase-S proteins in barley tissues and regarding previous data on effector regulation of the barley enzyme.
编码胚乳和叶片中该酶（分别为AGPase - S1和 - S2）同源物大亚基以及胚乳中小亚基蛋白（AGPase - B1）的大麦ADP - 葡萄糖焦磷酸化酶（AGPase）全长cDNA已在大肠杆菌中表达。AGPase - S1和 - S2的cDNA需要不同的诱导条件才能实现最大表达，并且它们编码免疫上不同的蛋白质。大肠杆菌产生的AGPase - S1与大麦粗胚乳提取物中的相应蛋白质具有相同的M(r)（58 kDa），而细菌产生的AGPase - S2（55 kDa）比大麦叶片制剂中的对应物（53 kDa）更大。从包含AGPase - S1和 - B1亚基cDNA的双构建体在大肠杆菌中表达的具有酶活性的AGPase，与大麦胚乳中的酶类似，对3 - 磷酸甘油酸的激活和无机磷酸盐的抑制不敏感。单独在细菌中表达时，AGPase - S1和 - B1均无活性。本文就大麦组织中未成熟AGPase - S蛋白细胞内靶向的可能机制以及关于大麦酶效应调节的先前数据进行了讨论。
