Department of Botany, University of California, Davis, California 95616.
Plant Physiol. 1974 Feb;53(2):297-303. doi: 10.1104/pp.53.2.297.
delta-Aminolevulinic acid was accumulated by greening cucumber (Cucumis sativus L. var. Alpha green) cotyledons, barley (Hordeum sativum var. Numar) leaves, and bean (Phaseolus vulgaris L. var. Red Kidney) leaves in the presence of various (14)C-labeled precursors and levulinic acid, a competitive inhibitor of delta-aminolevulinic acid dehydrase. The radioactivity in the accumulated delta-aminolevulinic acid was measured.The most effective labeled precursors were the 5 carbon dicarboxylic compounds glutamate, glutamine, and alpha-ketoglutarate. (14)C-Labeled glycine and succinate were relatively poor. The carboxyl and the methylene carbons of glycine were incorporated into delta-aminolevulinic acid to about equal extent. The carboxyl carbon of glutamate was incorporated almost as well as the internal carbons of the same compound. These results are inconsistent with the succinyl CoA-glycine succinyl transferase (delta-aminolevulinic acid synthetase) mode of delta-aminolevulinic acid production.When the same experiments were performed on turkey blood (which, as avian blood in general, possesses delta-aminolevulinic acid synthetase), delta-aminolevulinic acid was labeled most effectively from glycine-2-(14)C, moderately well from glycine-1-(14)C and glutamate-3,4-(14)C and not at all from glutamate-1-(14)C.It appears probable that greening higher plant tissues possess an alternate route to delta-aminolevulinic acid in which the carbon skeleton of glutamate (and alpha-ketoglutarate) is incorporated intact into the first committed metabolite of the chlorophyll pathway.
δ-氨基酮戊酸在存在各种 (14)C 标记前体和 δ-氨基酮戊酸脱水酶抑制剂戊烯酸的情况下，由绿化黄瓜（Cucumis sativus L. var. Alpha green）子叶、大麦（Hordeum sativum var. Numar）叶和菜豆（Phaseolus vulgaris L. var. Red Kidney）叶积累。测量积累的 δ-氨基酮戊酸中的放射性。最有效的标记前体是 5 碳二羧酸化合物谷氨酸、谷氨酰胺和 α-酮戊二酸。（14)C 标记的甘氨酸和琥珀酸相对较差。甘氨酸的羧基和亚甲基碳被掺入 δ-氨基酮戊酸的程度大致相同。谷氨酸的羧基碳原子几乎与同一化合物的内部碳原子一样被掺入。这些结果与琥珀酰辅酶 A-甘氨酸琥珀酰转移酶（δ-氨基酮戊酸合酶）模式的 δ-氨基酮戊酸生成不一致。当在火鸡血液（一般来说，鸟类血液具有 δ-氨基酮戊酸合酶）上进行相同的实验时，δ-氨基酮戊酸最有效地从甘氨酸-2-（14)C 标记，适度地从甘氨酸-1-（14)C 和谷氨酸-3,4-（14)C 标记，而从谷氨酸-1-（14)C 完全不标记。似乎绿化高等植物组织具有一种替代途径来生成 δ-氨基酮戊酸，其中谷氨酸（和 α-酮戊二酸）的碳骨架完整地掺入叶绿素途径的第一个关键代谢物中。
