Synthetic pathways to BCAAs in plants. 1, Thr deaminase. 2, Acetolactate synthase. 3, Acetolactate isomeroreductase. 4, Dihydroxy acid dehydratase. 5, BCAT. 6, 2-Isopropylmalate synthase. 7, Isopropylmalate isomerase. 8, Isopropylmalate dehydrogenase.