Fat Metabolism in Higher Plants: LVII. A Comparison of Fatty Acid-Synthesizing Enzymes in Chloroplasts Isolated from Mature and Immature Leaves of Spinach 1

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RESUMO

Chloroplasts isolated from immature leaves of spinach (Spinacia oleracea) differ in enzyme levels from those isolated from mature leaves. On a chlorophyll basis, immature chloroplast preparations had 5- to 6-fold higher capacity to synthesize fatty acids from 2-14C-acetate compared to plastids isolated from mature leaves. This difference was correlated with higher activities for the enzymes, acetyl coenzyme A synthetase, malonyl coenzyme A synthetase, acetyl coenzyme A carboxylase, and oleyl coenzyme A transferase in plastid pressates obtained from immature leaves. Disrupted chloroplast preparations from both mature and immature leaves retained the ability to incorporate 2-14C-acetate into fatty acids in a pattern similar to that by isolated chloroplasts. 2-14C-Acetate, 2-14C-acetyl coenzyme A, 2-14C-malonate, and 1,3-14C malonyl coenzyme A were readily incorporated into a number of fatty acids. Moreover, the synthesis of oleate by chloroplast pressates from these substrates was strongly inhibited by KCN, flavin adenine mononucleotides and dinucleotides, and anaerobic conditions, while linolenic acid synthesis was unaffected by these compounds.

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