Escherichia coli β-ketoacyl synthases (KAS) I and II carry out the elongation steps in fatty acid synthesis. Analyses using the cross-linker BSa [bis(sulphosuccinimidyl) suberate] and surfaceenhanced laser desorption/ionization-time-offlight MS disclosed only monomeric and dimeric forms of KAS II, whereas KAS I also forms higher multimers. The binding affinities for KAS I and KAS II to C14-acyl carrier protein (ACP) as well as for C14-ACP to KAS I and KAS II were determined. KAS I is sensitive to the ACP released during the transfer reaction, with 50% inhibition at 0.17 μM ACP close to the physiological concentration of ACP (0.13 μM). KAS I and II also differ in carrying out the decarboxylation step of the elongation reaction.
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© 2000 Biochemical Society
2000
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