Acetate Concentration and Chloroplast Pyruvate Dehydrogenase Complex in Spinacia oleracea Leaf Cells

Acetate concentration in spinach (Spinacia oleracea L.) leaf tissue has been determined by direct measurement in a leaf extract to oe 70 |xm or less. Additional evidence for such low acetate levels came from isotope dilution experiments where the [ l 14C]acetate incorporation into fatty acids was assayed using purified chloroplasts in the presence o f tissue extracts. Pyruvate dehydrogenase complex activity was shown to be present in spinach chloroplasts and was determined by a newly developed acetyl coenzyme A trapping system (100 nmol acetyl CoA formed per mg chloroplast protein per h). The problems o f acetyl CoA synthesis in both compart­ ments, chloroplasts and cytoplasm, are discussed in this context.