Phlorisovalerophenone synthase, a novel polyketide synthase from hop (Humulus lupulus L.) cones

• Published in: European journal of biochemistry Vol. 262; no. 2; pp. 612 - 616
• Main Authors: Paniego, N.B, Zuurbier, K.W.M, Fung, S.Y, Heijden, R. van der, Scheffer, J.J.C, Verpoorte, R
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01-06-1999
• Subjects: Acyltransferases - chemistry; Acyltransferases - isolation & purification; Amino Acid Sequence; Catalysis; chalcone synthase; characterization; Chromatography, Ion Exchange; Electrophoresis, Polyacrylamide Gel; hop bitter acids; Humulus lupulus; Molecular Sequence Data; phlorisovalerophenone synthase; polyketide synthase; purification; Rosales - enzymology
• ISSN: 0014-2956; 1432-1033
• DOI: 10.1046/j.1432-1327.1999.00444.x

Phlorisovalerophenone synthase (VPS), a novel aromatic polyketide synthase, was purified to homogeneity from 4.2 mg protein extract obtained from hop (Humulus lupulus L.) cone glandular hairs. The enzyme uses isovaleryl‐CoA or isobutyryl‐CoA and three molecules of malonyl‐CoA to form phlorisovalerophenone or phlorisobutyrophenone, intermediates in the biosynthesis of the hop bitter acids (α‐ and β‐acids). VPS is an homodimeric enzyme, with subunits of 45 kDa. The pI of the enzyme was 6.1. Km values of 4 µm for isovaleryl‐CoA, 10 µm for isobutyryl‐CoA and 33 µm for malonyl‐CoA, were found. The amino‐acid sequences of two peptides, obtained by digestion of VPS, showed that the enzyme is highly homologous to plant chalcone synthases. The functional and structural relationship between VPS and other aromatic polyketide synthases is discussed.