Hydrolysis of Acyl-ACPs By PedC

The a-methyl-P-hydroxyl acyl-ACP (45) is in the correct stereoconfiguration to act as a substrate mimic of the intermediate at ACP2 in pederin biosynthesis. Incubation of (10) with PedC yielded no measurable hydrolysis, implying that an a,P-branched substrate provides sufficient steric bulk to prevent hydrolysis under the conditions employed. The 6-methyltetrahydro-27f-pyran-ACP (46) was synthesised to represent the ACP4 intermediate in pederin biosynthesis. PedC was imable 

It has been proposed that the proofreading ability of PedC could be harnessed to elucidate the mechanistic steps in the biosynthesis of other biosynthetic pathways [20]. This requires PedC to be sufficiently promiscuous with regard to its specificity to hydrolyse unnatural intermediates from other clusters [16, 20]. Therefore, in addition to the acyl-ACP mimics of the pederin intermediates, we also tested oxazole-ACP (47), present as an intermediate of both rhizoxin and chi-vosazol biosynthesis. No hydrolytic activity was observed towards the oxazole-ACP, suggesting that the five-membered heterocycle is not tolerated by the PedC active site in this assay. 

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