Figure 1.

The tocopherol biosynthetic pathway in plants. Dashed arrows represent multiple steps. Enzymes are indicated by circled numbers: 1, HGA phytyltransferase (HPT); 2, p-hydroxyphenyl pyruvate dioxygenase (HPPD); 3, HGA dioxygenase; 4, geranylgeranyl diphosphate reductase (GGDR); 5, geranylgeranyl diphosphate synthase (GGPS); 6, 1-deoxy-d-xylulose-5-phosphate synthase (DXPS); 7, 2-methyl-6-phytyl-1,4-benzoquinol methyltransferase (MPBQ); 8, tocopherol cyclase (TC); and 9, γ-tocopherol methyltransferase (γ-TMT).