Action of ACC Inhibitors

Two key papers [25, 26] established that the two types of ACC enzymes in plant correlated with the differential inhibition of the new herbicides represented by two classes the AOPPs and the CHDs, which are strong inhibitors of the multi-domain plastid ACC found in grasses. Prokaryotic-type multisubunit plastid ACC is resistant to these herbiddes, as are eukaryote ACCs from animals and yeast. 

This observation confirms that an inhibitor of the CT domain is suffident to block the fundion of the ACC (Fig. 9.2), and it establishes this domain as a valid target for the development of inhibitors against these enzymes. 

Interaction of AOPP and CHD inhibitors is an important tool to understand plant ACC biochemistry, and the use of chimeric genes was a significant step forward in the elucidation of differential adivities for different chemical dasses [12, 31]. Gomicld et al. showed that some determinants of sensitivity were located on a 400-amino acid fragment of wheat plastidic ACC in the CT domain [12]. The chimeric genes consisted of the yeast GALIO promoter, the yeast ACCl leader and the wheat acetyl-CoA carboxylase cDNA. 

The yeast ACCl 3 -tail was used to complement ACCl null mutation. These genes encode a full-length plastid enzyme, with or without the putative chloro-plast transit peptide, as well as five chimeric cytosolic/plastid proteins (Fig. 9.3). 

Combining this yeast gene replacement strains system with kinetics values from purified plastidic proteins together provide a convenient tool to study herbicide interaction with the enzyme and a powerfiil screening system for new inhibitors. 

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