Subcellular distribution of acetyl-coenzyme A carboxylase in mesophyll cells of barley and sorghum leaves.

The subcellular distribution of acetyl-CoA carboxylase [acetyl-CoA-carbon dioxide ligase (ADP-forming), EC 6.4.1.2] was determined in mesophyll protoplasts isolation from barley, a C3 plant, and sorghum, a C4 plant. In both species, all of the mesophyll acetyl-CoA carboxylase was demonstrated to be chloroplastic. In barley leaves and mesophyll protoplasts, a single biotinyl protein of 60,000 Da was identified by a modified Western-blotting procedure. The subcellular distribution of this biotinyl protein was identical to that found for acetyl-CoA carboxylase. These results are discussed in relation to the compartmentation of reactions requiring malonyl-CoA as a substrate.