Submitted to: Plant Physiology Supplement
Publication Type: Abstract only
Publication Acceptance Date: 7/27/1996
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Acetyl-coenzyme A carboxylase (ACCase) is a biotin containing enzyme that catalyzes the ATP dependent carboxylation of acetyl CoA to form malonyl CoA. There is increasing evidence that dicots contain both a multi subunit, "prokaryotic type" ACCase as well as multi functional, "eukaryotic type" ACCases. We investigated whether both types of ACCases were present in soybean seeds and leaves. Crude extracts were obtained from the embryo and seed coats of soybean seeds 40 days after flowering. Extracts were applied to a Q Sepharose column and fractionated with a KCl (0 to 500 mM) gradient. For embryos, two peaks of ACCase activity were detected. One peak, which eluted at approximately 300 mM KCl, contained the multi subunit ACCase (38 kDa biotinylated subunit). The second peak, which eluted at approximately 400 mM KCl, contained the multi functional ACCase (210 kDa subunit). For extracts from the seed coat, a single peak of ACCase activity was detected. This peak contained a multi functional ACCase (210 kDa subunit) that eluted at approximately 300 mM KCl. In an effort to further characterize the multi subunit ACCase, chloroplasts were isolated from 10 to 12 day old soybean leaves using a continuous Percoll (10 to 80%) gradient. Purified chloroplasts contained the 38 kDa subunit of the multi subunit ACCase, but not the 210 kDa subunit of the multi functional ACCase. Attempts at further purification of the multi subunit ACCase from isolated chloroplasts resulted in dissociation of the enzyme and loss of activity. However, combining the 0 to 15% and 35 to 50% ammonium sulfate fractions resulted in recovery of activity. The results of further studies of the multi subunit ACCase will be reported.