Genes and Enzymes Involved in Caffeic Acid Biosynthesis in the Actinomycete Saccharothrix espanaensis

Abstract

ABSTRACT The saccharomicins A and B, produced by the actinomycete Saccharothrix espanaensis , are oligosaccharide antibiotics. They consist of 17 monosaccharide units and the unique aglycon N -( m , p -dihydroxycinnamoyl)taurine. To investigate candidate genes responsible for the formation of trans-m , p -dihydroxycinnamic acid (caffeic acid) as part of the saccharomicin aglycon, gene expression experiments were carried out in Streptomyces fradiae XKS. It is shown that the biosynthetic pathway for trans -caffeic acid proceeds from l -tyrosine via trans-p -coumaric acid directly to trans -caffeic acid, since heterologous expression of s am8 , encoding a tyrosine ammonia-lyase, led to the production of trans-p -hydroxycinnamic acid (coumaric acid), and coexpression of sam8 and sam5 , the latter encoding a 4-coumarate 3-hydroxylase, led to the production of trans-m , p -dihydroxycinnamic acid. This is not in accordance with the general phenylpropanoid pathway in plants, where trans-p -coumaric acid is first activated before the 3-hydroxylation of its ring takes place.