Figure 2. Comparison of radioactive and spectrophotometric assays in measuring activities of reconstituted fatty acid synthases.
(A) Reference FAS, consisting of 1 μM FabABDFGHIZ, 10 μM holo-ACP, and 10 μM TesA. (B) Optimized FAS, consisting of 1 μM FabABDFGH, 10 μM FabIZ, 30 μM holo-ACP, and 30 μM TesA. Reaction conditions were otherwise identical: 100 μM acetyl-CoA, 500 μM malonyl-CoA, and 1.3 mM NADPH. Under optimal conditions, the initial rate of fatty acid production was missed when a radioactive assay was used. See also Table 1 for a comparison of the measured rate constants.