The pathway of sinapate ester biosynthesis in Arabidopsis

The pathway of sinapate ester biosynthesis in Arabidopsis. Multiple steps are required for the conversion of Phe to sinapic acid via p-coumaroyl-CoA. The enzymes required for the synthesis of sinapate esters in developing seeds are SGT and SCT. Upon germination, sinapoylcholinesterase (SCE) catalyzes the hydrolysis of seed reserves of sinapoylcholine, and SGT and SMT convert the released sinapate into sinapoylmalate. SST catalyzes the conversion of two molecules of sinapoyl-Glc to 1,2-disinapoyl-Glc and compound 1, a biosynthetic route that is predominant in etiolated seedlings. Dashed arrows indicate one possible route to the biosynthesis of compound 1, a reaction dependent upon SST. The action of SAT is required for the sinapoylation of Arabidopsis anthocyanins. Double arrows proceeding from p-coumaroyl-CoA indicate the biosynthesis of the cyanidin derivative via flavonoid metabolism and the subsequent acylation of the anthocyanin, presumably by a p-coumaroyl-CoA-dependent acyltransferase. This biosynthetic pathway yields one possible substrate for SAT, 3-O-(6-O-p-coumaroyl-2-O-β-d-xylopyranosyl-β-d-glucopyranosyl)-5-O-(6-O-malonyl-β-d-glucopyranosyl) cyanidin (A5; nomenclature from ), sinapoylation of which would result in the production of 3-O-[6-O-(4-O-β-d-glucopyranosyl-p-coumaroyl)-2-O-(2-O-sinapoyl-β-d-xylopyranosyl)-β-d-glucopyranosyl]-5-O-(6-O-malonyl-β-d-glucopyranosyl) cyanidin (A11).

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Related Arabidopsis Serine Carboxypeptidase-Like Sinapoylglucose Acyltransferases Display Distinct But Overlapping Substrate Specificities. (2007) Christopher M. Fraser, et al. Plant Physiol. 2007 Aug;144(4):1986-1999. Figure: F1. All organisms Drosophila melanogaster Homo sapiens

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