Purification of plastids from higher-plant roots.

A procedure is described for the purification of plastids from the roots of Pisum sativum L. The preparations obtained are appreciably free of contamination by other particles as judged by the distribution of organelle-specific marker enzymes and by electron microscopy. Latency of glutamate synthase (EC 2.6.1.53) within these preparations indicates that the plastids obtained are 90-95% intact, whilst the resistance of this enzyme, and glucose-6-phosphogluconate dehydrogenase (EC 1.1.1.43) to tryptic digestion in unlysed organelles indicates that they are at least 70-85% intact and may be suitable for studies of metabolite transport.