l h e intracellular localization of transaldolase, transketolase, ribose-5-phosphate isomerase, and ribulose-5-phosphate epimerase was reexamined in spinach (Spinacia oleracea 1,) leaves. We found a highly predominant if not exclusive localization of these enzyme activities in chloroplasts isolated by isopyknic centrifugation in sucrose gradients. Clucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, glucose phosphate isomerase, and triose phosphate isomerase activity was present in the chloroplast fraction but showed additional activity in the cytosol (supernatant) fraction attributable to the cytosol-specific isoforms known to exist for these enzymes. Anion-exchange chromatography of proteins of crude extracts on diethylaminoethyl-Fractogel revealed only a single enzyme each for transaldolase, transketolase, ribose-5-phosphate isomerase, and ribulose-5-phosphate epimerase. The data indicate that chloroplasts of spinach leaf cells possess the complete complement of enzymes of the oxidative pentose phosphate pathway (OPPP), whereas the cytosol contains only the first two reactions, contrary to the widely held view that plants generally possess a cytosolic OPPP capable of cyclic function. l h e chloroplast enzymes transketolase, ribose-5-phosphate isomerase, and ribulose-5-phosphate epimerase appear to be amphibolic for the Calvin cycle and OPPP.

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The AutoMicrobic system Yeast Biochemical Card (Vitek Systems, Inc., subsidiary of McDonnell Douglas, Hazelwood, Mo.), a fully automated and computerassisted method for identifying seven yeast genera based on 26 biochemical

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