Reductant for glutamate synthase in generated by the oxidative pentose phosphate pathway in non‐photosynthetic root plastids

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Abstract
Summary: Purified pea root plastids were supplied with glutamine, 2‐oxoglutarate and phosphorylated sugars. Formation of glutamate was linear for 75 min and dependent upon the intactness of the organelle. Glucose‐6‐phosphate and ribose‐5‐phosphate were the most effective substrates in supporting glutamate synthesis. Flux through the oxidative pentose phosphate pathway during glutamate synthesis in purified plastids was followed by monitoring the release of 14CO2 from [1‐14C]glucose‐6‐phosphate. 14CO2 evolution from C‐1 was dependent upon the presence of both glutamine and 2‐oxoglutarate and could be inhibited by the application of azaserine. The data are discussed in view of the role of the oxidative pentose phosphate pathway in non‐photosynthetic plastids.