Localization of Carboxydismutase & Triosephosphate Dehydrogenases in Chloroplasts

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Abstract
A quantitative method has been developed to calculate the distribution in the cell of soluble enzymes from data on enzyme activities in different cell fractions and from the protein distribution within the cell. Chloroplasts were isolated in a nonaqueous procedure from frozen dried leaves of Nicotiana tabacum, Tetragonia expansa, Secale cereale, Trifolium repens, Vicia faba and Spinacia oleracea, and enzyme activities were determined in the chloroplast fraction, in the residual material, and in whole tissue. Carboxydismutase and TPN dependent triosephosphate dehydrogenase were found to be located exclusively or nearly exclusively in the chloroplasts, while DPN dependent triosephosphate dehydrogenase was distributed between chloroplasts and the cytoplasm. About 20-40% of the latter enzyme resides in the chloroplasts.