Department of Botany and Plant Pathology, Iowa State University, Ames, Iowa 50011.
Plant Physiol. 1978 Apr;61(4):654-7. doi: 10.1104/pp.61.4.654.
The objective of these experiments was to determine the fate of tritium from the 5 position of proline and to assess the validity of its loss to H(2)O as a measure of proline oxidation. When [5-(3)H]proline was fed to barley (Hordeum vulgare) leaves, tritium was recovered in H(2)O and metabolites such as glutamate, glutamine, organic acids, aspartate, asparagine, and gamma-aminobutyrate. Collectively these metabolites, which are oxidation products of proline, accounted for 8% of the (3)H recovered after 5 hours. In spite of the amount recovered in metabolites, the rates of proline oxidation estimated by measuring (3)H(2)O recovery from [5-(3)H]proline were only slightly lower than rates estimated by incorporation of (14)C into oxidized products and loss of (14)C from total proline. Therefore, (3)H(2)O recovery from [5-(3)H]proline is useful in assessing the effects of stress on proline metabolism.Water stress inhibited proline oxidation, as reported previously. In addition, a reconversion of proline oxidation products to proline occurred in stressed leaves. This observation probably indicates a breakdown in cellular compartmentation of proline synthesis and proline oxidation.
这些实验的目的是确定脯氨酸 5 位的氚的命运，并评估其损失到 H2O 作为脯氨酸氧化的度量的有效性。当 [5-(3)H]脯氨酸被喂食到大麦（Hordeum vulgare）叶片时，氚被回收在 H2O 和代谢物中，如谷氨酸、谷氨酰胺、有机酸、天冬氨酸、天冬酰胺和γ-氨基丁酸。这些代谢物是脯氨酸的氧化产物，它们共同占 5 小时后回收的 (3)H 的 8%。尽管在代谢物中回收的量很大，但通过测量 [5-(3)H]脯氨酸中 (3)H2O 的回收来估计的脯氨酸氧化速率仅略低于通过将 (14)C 掺入氧化产物和从总脯氨酸中损失 (14)C 来估计的速率。因此，从 [5-(3)H]脯氨酸中回收 (3)H2O 可用于评估应激对脯氨酸代谢的影响。如前所述，水分胁迫抑制了脯氨酸的氧化。此外，在应激叶片中发生了脯氨酸氧化产物向脯氨酸的再转化。这一观察结果可能表明脯氨酸合成和脯氨酸氧化的细胞区室化的破坏。
