Description:
<p>• Polyprenylated acylphloroglucinol derivatives, such as xanthones, are natural plant products with interesting pharmacological properties. They are difficult to synthesize chemically. Biotechnological production is desirable but it requires an understanding of the biosynthetic pathways.</p>
<p>• cDNAs encoding membrane-bound aromatic prenyltransferase (aPT) enzymes from <italic>Hypericum sampsonii</italic> seedlings (<italic>Hs</italic>PT8px and <italic>Hs</italic>PTpat) and <italic>Hypericum calycinum</italic> cell cultures (<italic>Hc</italic>PT8px and <italic>Hc</italic>PTpat) were cloned and expressed in <italic>Saccharomyces cerevisiae</italic> and <italic>Nicotiana benthamiana</italic>, respectively. Microsomes and chloroplasts were used for functional analysis.</p>
<p>• The enzymes catalyzed the prenylation of 1,3,6,7-tetrahydroxyxanthone (1367THX) and/or 1,3,6,7-tetrahydroxy-8-prenylxanthone (8PX) and discriminated nine additionally tested acylphloroglucinol derivatives. The transient expression of the two <italic>aPT</italic> genes preceded the accumulation of the products in elicitor-treated <italic>H</italic>. <italic>calycinum</italic> cell cultures. C-terminal yellow fluorescent protein fusions of the two enzymes were localized to the envelope of chloroplasts in <italic>N</italic>. <italic>benthamiana</italic> leaves.</p>
<p>• Based on the kinetic properties of <italic>Hs</italic>PT8px and <italic>Hs</italic>PTpat, the enzymes catalyze sequential rather than parallel addition of two prenyl groups to the carbon atom 8 of 1367THX, yielding <italic>gem</italic>-diprenylated patulone under loss of aromaticity of the <italic>gem</italic>-dialkylated ring. Coexpression in yeast significantly increased product formation. The patulone biosynthetic pathway involves multiple subcellular compartments. The aPTs studied here and related enzymes may be promising tools for plant/microbe metabolic pathway engineering.</p>