Evidence for a glycolate transporter in the envelope of pea chloroplasts

Glycolate excretion by chloroplasts is essential to the process of photorespiration. Previous transport studies on intact chloroplasts have failed to find evidence for carrier‐mediated transport of glycolate. The rate of glycolate uptake, when measured by a rapid silicone oil centrifugation method, saturates at high glycolate concentrations. This rapid glycolate uptake is inhibited by pretreatment of the chloroplasts with N‐ethylmaleimide, an inhibition prevented by glycolate. Glyoxylate and glycerate inhibit glycolate uptake when present in the assay medium. These results suggest the existence of a glycolate transporter in the chloroplast envelope.