Development of a Multienzyme Cascade for Salvianolic Acid A Synthesis from l-Tyrosine.

Salvianolic acid A (SAA) has an important application value for preventing and treating cardiovascular diseases. In this study, we developed a novel multienzyme cascade system for the efficient biosynthesis of SAA, utilizing l-tyrosine (l-Tyr) as a cost-effective and stable starting material. The cascade system incorporated four enzymes: membrane-bound l-amino acid deaminase from (ml-AAD), d-lactate dehydrogenase from (d-LDH), 4-hydroxyphenylacetate 3-hydroxylase from (HpaBC), and formate dehydrogenase from N10 (FDH). All reaction steps in the cascade system were thermodynamically favorable. In addition, to avoid generating an unstable intermediate (3,4-dihydroxyphenyl-pyruvate, DHPPA), which was produced owing to the promiscuity of HpaBC and d-LDH, we performed the cascade system according to the reaction sequence of deamination, chiral reduction, and -hydroxylation. Under optimized conditions, the developed cascade system yielded 81.67 mM SAA from an initial concentration of 100 mM l-Tyr, corresponding to a yield of 81.67%.