Department of Biology and Institute of Biochemistry, Carleton University, Ottawa, Ontario K1S 5B6 Canada.
Plant Physiol. 1985 Jun;78(2):334-7. doi: 10.1104/pp.78.2.334.
In pea leaves, much of the metabolism of imported asparagine is by transamination. This activity was previously shown to be localized in the peroxisomes, suggesting a possible connection between asparagine and photorespiratory nitrogen metabolism. This was investigated by examination of the transfer of (15)N from the amino group of asparagine, supplied via the transpiration stream, in fully expanded pea leaves. Label was transferred to aspartate, glutamate, alanine, glycine, serine, ammonia, and glutamine (amide group). Under low oxygen (1.8%), or in the presence of alpha-hydroxy-2-pyridine methanesulfonic acid (an inhibitor of glycolate oxidase, a step in the photorespiratory formation of glyoxylate), there was a substantial (60-80%) decrease in transfer of label to glycine, serine, ammonia, and glutamine. Addition of isonicotinyl hydrazide (an inhibitor of formation of serine from glycine) caused a 70% decrease in transfer of asparagine amino nitrogen to serine, ammonia, and glutamine, while a 4-fold increase in labeling of glycine was observed. The results demonstrate the involvement of asparagine in photorespiration, and show that photorespiratory nitrogen metabolism is not a closed cyclic process.
在豌豆叶片中，进口天冬酰胺的大部分代谢是通过转氨基作用进行的。先前的研究表明，这种活性定位于过氧化物酶体中，这表明天冬酰胺和光呼吸氮代谢之间可能存在联系。通过检查通过蒸腾流供应的天冬酰胺的氨基氮在完全展开的豌豆叶片中的转移，研究了这一点。标记被转移到天冬氨酸、谷氨酸、丙氨酸、甘氨酸、丝氨酸、氨和谷氨酰胺（酰胺基）。在低氧（1.8%）下，或在α-羟基-2-吡啶甲烷磺酸（光呼吸生成乙醛酸的步骤中乙醛酸氧化酶的抑制剂）存在下，标记向天冬氨酸、谷氨酸、丙氨酸、甘氨酸、丝氨酸、氨和谷氨酰胺的转移有很大（60-80%）减少。异烟酰肼（甘氨酸转化为丝氨酸的抑制剂）的添加导致天冬酰胺氨基氮向天冬氨酸、氨和谷氨酰胺的转移减少了 70%，而甘氨酸的标记增加了 4 倍。结果表明天冬酰胺参与了光呼吸，并且表明光呼吸氮代谢不是一个封闭的循环过程。
