Figure 4.

PtAAS1 and PtAADC1 are interconvertible by the mutation of a single amino acid and are likely derived by tandem gene duplication. A, The recombinant proteins PtAAS1, PtAADC1, and the corresponding mutant enzymes PtAAS1 (F338Y) and PtAADC1 (Y338F) were incubated with l-Phe in the presence of PLP. Enzyme products were analyzed using GC-MS (2-phenylacetaldehyde) and LC-MS/MS (2-phenylethylamine). B, PtAADC1 and PtAAS1 form a gene cluster on chromosome 13. Both genes are oriented in the same direction and there are no coding regions between them. Sequence data were retrieved from the P. trichocarpa Genome Assembly (version 3.0; www.phytozome.net; Tuskan et al., 2006).