The 2.4 A crystal structure of the vitamin B6-dependent enzyme 1-aminocyclopropane-1-carboxylate (ACC) synthase is described. This enzyme catalyses the committed step in the biosynthesis of ethylene, a plant hormone that is responsible for the initiation of fruit ripening and for regulating many other developmental processes. ACC synthase has 15 % sequence identity with the well-studied aspartate aminotransferase, and a completely different catalytic activity yet the overall folds and the active sites are very similar. The new structure together with available biochemical data enables a comparative mechanistic analysis that largely explains the catalytic roles of the conserved and non-conserved active site residues. An external aldimine reaction intermediate (external aldimine with ACC, i.e. with the product) has been modeled. The new structure provides a basis for the rational design of inhibitors with broad agricultural applications.

• PMID: 10610793
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Journal Article | Research Support, Non-U.S. Gov't | Research Support, U.S. Gov't, P.H.S.

Authors

Capitani G, Hohenester E, Feng L, Storici P, Kirsch JF, Jansonius JN

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