A specific translocator for oxaloacetate transport in chloroplasts

Evidence is provided that oxaloacetate is taken up by chloroplasts from maize and spinach leaves by a high‐affinity carrier. Apparent K m values for oxaloacetate are about 45 and 9 μM, respectively. Uptake was measured by following [4‐ 14 C]oxaloacetate reduction in illuminated chloroplasts. With maize chloroplasts the rates of uptake were sufficient to account for photosynthesis. This carrier had a very low affinity for malate and 2‐oxoglutarate. Ratios of the K i , for malate or 2‐oxoglutarate to the K m for oxaloacetate were about 150 and 50, respectively.