Hydroxycinnamic acid transferases

Bokern, M., Heuer, S. and Strack, D. (1992) Hydroxycinnamic acid transferases in the biosynthesis of acylated betacyanins purification and characterization from cell cultures of Chenopodium rubrum and occurrence in some other members of the Caryophyllales. Bot. Acta, 105, 146-51. 

Alkaloids 36-41 were isolated from Lupinus luteus L. seedlings. They are considered to be lupinine esters with 4-hydroxycinnamic acids (94-100). The structures of these new alkaloids were elucidated on the basis of H NMR, MS, and chemical and enzymatic transformations. All these alkaloids were obtained from lupinine and hydroxycinnamic acid by two enzymatic systems (96-97) ligase catalyzed formation of the CoA-thioester, and transferase catalyzed lupinine ester formation from the CoA-thioester. 

Moreover, hydroxycinnamate-CoAs can conjugate with organic acids. In the biosynthesis of sugar derivatives of hydroxycinnamic acids, the transfer of glucose from uridine diphosphoglucose to hydroxyciimamic acid is catalyzed by glucosyl transferase [8, 16]. 

Methylation of caffeic acid leads to the formation of femlic acid, which, together with p-coumaric acid, are the precursors of lignins. The methylation is catalyzed by an 0-methyltransferase. Caffeic acid is the substrate for the rare 5-hydroxyfemlic acid, which yields sinapic acid as a result of O-methylation. The formation of hydroxyciimamic acid derivatives requires the formation of hydroxycinnamate-CoAs (e.g., p-coumaroyl-CoA) catalyzed by hydroxyciimamoyl-CoA ligases or by the action of 0-glycosyl transferases. 

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