Metabolism of tyrosine and tryptophan--new genes for old pathways

Tyrosine and tryptophan are precursors for the plant defense compounds dhurrin and indole glucosinolates, respectively. In addition, tryptophan is a precursor for the essential phytohormone indole-3-acetic acid. Recent advances in understanding the biosynthesis of these compounds have come from the characterization of enzymes that catalyze the N-hydroxylation of the precursor amino acid to the oxime intermediate. Furthermore, enzymes catalyzing subsequent biosynthetic steps have also been identified.