Evolution of Acyltransferase Genes: Origin and Diversification of the BAHD Superfamily of Acyltransferases Involved in Secondary Metabolism

Enzymatic acylation is a widespread substitution reaction that is notably involved in the diversification of natural substances produced by plant secondary metabolism. Acylation may also trigger nonenzyme-catalyzed reactions in natural product biosynthesis. The glycerophospholipid acyltransferase (CoA)–dependent acyltransferases are also much diversified with respect to their molecular mass, oligomeric structure, and amino acid sequences. Several distinct classes of enzymes have been characterized among prokaryotes and animals, and many do not show any sequence conservation with other acyltransferases described in this chapter. The chapter describes a recently characterized acyltransferase superfamily from higher plants and fungi. The evolutionary aspects of this gene superfamily are discussed in the chapter, with a special emphasis on the acyltransferases of Arabidopsis thaliana , whose genome is being completely sequenced. Clustering of genes that participate in a common metabolic pathway—a general feature of prokaryotic gene organization—has been observed in filamentous fungi for many dispensable metabolic pathways (rare nutrient utilization and natural product biosynthesis).