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. 2016 Jul 19;4:58. doi: 10.3389/fbioe.2016.00058

Figure 1.

Figure 1

Simplified lignin biosynthetic pathway and the methionine salvage cycle (or Yang cycle). Enzymatic steps consuming AdoMet in the lignin biosynthetic pathway are catalyzed by CCoAOMT and COMT (A). The metabolic shunt mediated by AdoMetase in the Yang cycle is shown in red (B). Abbreviations: ACC, 1-aminocyclopropanecarboxylate; AdoHCY, S-adenosylhomocysteine; AdoMet, S-adenosylmethionine; CCoAOMT, caffeoyl CoA O-methyltransferase; COMT, caffeic acid O-methyltransferase; CY, cystathionine; dcAdoMet, decarboxylated AdoMet; DHKMP, 1,2-dihydroxy-3-keto-5-methylthiopentene; DKPP, 2,3-diketo-5-methylthiopentyl-1-phosphate; ETHY, ethylene; HCY, homocysteine; HKMPP, 2-hydroxy-3-keto-5-methylthiopentenyl-1-phosphate; HS, homoserine; KMTB, α-ketomethylthiobutyrate; Met, methionine; MTA, methylthioadenosine; MTR, 5-methylthioribose; MTRP, 5-methylthioribose-1-phosphate; MTRuP, methylthioribulose-1-phosphate; NA, nicotianamide; PHS, O-phosphohomoserine; SPD, spermidine; THR, threonine. a, NA synthase; b, AdoMet decarboxylase; c, SPD synthase; d, ACC synthase; e, ACC oxidase; ①, MTA nucleosidase; ②, MTR kinase; ③, MTRP isomerase; ④, MTRuP dehydratase; ⑤, DKPP enolase; ⑥, HKMPP phosphatase; ⑦, DHKMP dioxygenase; ⑧, KMTB aminotransferase. ➊ HS kinase; ➋, CY synthase; ➌, CY β-lyase; ➍, Met synthase; ➎, Thr synthase.