Walker J L, Oliver D J
Arch Biochem Biophys. 1986 Aug 1;248(2):626-38. doi: 10.1016/0003-9861(86)90517-5.
The rates of mitochondrial glycine oxidation estimated by CO2-release and glycine-bicarbonate exchange activities in fully greened tissues are approximately 10 times greater than those of etiolated pea leaves and potato tuber mitochondria. The release of CO2 from glycine in intact mitochondria isolated from dark-grown and nonphotosynthetic tissues was sensitive to inhibitors of mitochondrial electron transport, glycine transport, and glycine decarboxylase activities. The CO2-release and glycine-bicarbonate exchange activities in crude mitochondrial protein extracts from light-grown versus dark-grown tissues exhibited light/dark ratios of 12 and 21, respectively. This suggests that the differences in capacity to oxidize glycine reside with the glycine decarboxylase enzyme complex itself. The complex is composed of four subunit enzymes, the P, H, T, and L proteins, which can be isolated individually and reconstituted into the active enzyme. The activities of P and T proteins were at least 10 times higher in fully greened pea leaves than in the etiolated tissue, while the H and L protein activities were four times higher in these same tissues. The levels of P and T proteins detected immunochemically were substantially lower in total mitochondrial extracts prepared from leaves of dark-grown pea seedlings. Labeling of whole pea seedlings and in vitro protein synthesis with isolated mitochondria indicated that the entire glycine decarboxylase enzyme complex is cytoplasmically synthesized and therefore encoded by the nucleus. Polypeptides synthesized from total leaf polyadenylated mRNA isolated from leaves of both the dark-grown and light-treated peas indicated the presence of P protein. This implies that translatable messages for this enzyme are present at some level throughout leaf development.
通过完全绿化组织中二氧化碳释放和甘氨酸 - 碳酸氢盐交换活性估算的线粒体甘氨酸氧化速率，大约是黄化豌豆叶片和马铃薯块茎线粒体的10倍。从黑暗生长的非光合组织中分离出的完整线粒体中，甘氨酸释放的二氧化碳对线粒体电子传递、甘氨酸转运和甘氨酸脱羧酶活性的抑制剂敏感。来自光照生长与黑暗生长组织的粗线粒体蛋白提取物中的二氧化碳释放和甘氨酸 - 碳酸氢盐交换活性，光/暗比分别为12和21。这表明甘氨酸氧化能力的差异存在于甘氨酸脱羧酶复合体本身。该复合体由四种亚基酶组成，即P、H、T和L蛋白，它们可以单独分离并重新组装成活性酶。完全绿化的豌豆叶片中P和T蛋白的活性至少比黄化组织高10倍，而在相同组织中H和L蛋白的活性高4倍。从黑暗生长的豌豆幼苗叶片制备的线粒体总提取物中，免疫化学检测到的P和T蛋白水平显著较低。对整个豌豆幼苗进行标记以及用分离的线粒体进行体外蛋白质合成表明，整个甘氨酸脱羧酶复合体是在细胞质中合成的，因此由细胞核编码。从黑暗生长和光照处理的豌豆叶片中分离的总叶多聚腺苷酸化mRNA合成的多肽表明存在P蛋白。这意味着在叶片发育的整个过程中，该酶的可翻译信息在一定水平上存在。
