Metabolism of trans‐3‐Hexadecenoic Acid in Broad Bean

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Abstract
1 Broad bean (Vicia faba) leaves contain rather high concentrations (about 4% of total fatty acids) of the trans-3-hexadecenoic acid. 2 Amounts of the acid increase with the age of the leaves and are absent from etiolated tissue. 3 Changes in the levels of trans-Δ3-hexadecenoic acid can be produced by subjecting the intact plants to various light/dark periods. 4 Chloroplasts isolated from broad-bean leaves show high rates of fatty acid synthesis from [1-14C]acetate. Synthesis is dependent on coenzyme A and ATP but is insensitive to the addition of exogenous acyl carrier protein. 5 The pattern of acids made includes about 20% palmitic, 5% hexadecenoic, 10% stearic and 60% oleic. trans-3-Hexadecenoic acid synthesis was most active in chloroplasts from plants exposed to the dark for 5 days and light for 3 days. 6 Arsenite addition inhibited stearate formation by isolated chloroplasts but resulted in a two-fold stimulation of overall synthesis. 7 The rate of fatty acid synthesis by isolated chloroplasts paralleled the changes in endogenous trans-3-hexadecenoic acid levels in the leaves from which they were isolated.