Metabolism of α-Ketoglutarate by Roots of Woody Plants

The uptake and metabolism of alpha-ketoglutarate-5-(14)C by peach, apple, and privet root tissues were studied over various time intervals. As much as 80% of the absorbed (14)C appeared as (14)CO(2) in 320 minutes in peach roots. Apple and privet roots were less effective in this conversion with the bulk of the (14)C found in the organic acid fraction. This indicates differences in organic acid metabolism among species of woody plants.The (14)C accumulated in malate earlier and in larger quantities than in citrate. Both glutamate and aspartate were labeled in 10 minutes and glutamate was labeled as early as 3 minutes. The labeling pattern does not clearly distinguish between the synthesis of glutamate by glutamic dehydrogenase or by transamination with oxaloacetate.The rapid metabolism of alpha-ketoglutarate to glutamate by the 3 species studied indicates the presence of enzyme systems important in amino acid synthesis in the roots of woody plants.