GLUTAMINE AND GLUTAMATE TRANSPORT IN CYANOPHORA-PARADOXA

The present investigation showed that isolated cyanelles from Cyanopho ra paradoxa selectively enriched glutamine from the external medium, w hereas glutamate poorly penetrated into these organelles. Glutamine up take proceeded in two phases, presumably involving a low and a high af finity system. The uptake of glutamine was significantly enhanced by 2 -oxoglutarate and light. Inhibitor experiments indicated that glutamin e and 2-oxoglutarate were converted to glutamate by a ferredoxin-depen dent glutamate synthase (GOGAT) reaction inside the cyanelles, and the glutamate formed at best slowly left these organelles. Such results w ere obtained independently of each other by measuring either the C-14- glutamine uptake or the 2-oxoglutarate and glutamine-dependent O-2 evo lution. Glutamine is suggested to be the N-compound which is supplied to the eukaryotic host. Glutamine could be exported jointly with 2-oxo glutarate, possibly employing a common carrier. Cyanelles have apparen tly evolved glutamine (and oxoglutarate) carrier(s) with properties no t yet described for any other organism.