Purification and substrate specifities of hydroxycinnamate: CoA ligase from anthocyanin-containing and anthocyanin-free carrot cells

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Abstract
Callus cells of Daucus carota L. have different phenylpropanoid pathways depending on the medium composition. Cells propagated on a medium with gibberellic acid do not accumulate cyanidin but incorporate [14C]phenylalanine into chlorogenic acid at a high rate. Cells grown on a medium free of gibberellic acid accumulate cyanidin in very large amounts. We here describe partial purification of hydroxycinnamate: CoA ligase, and its properties in these two cell lines. The enzymes extracted from the two cell populations had different substrate specifities: for that from anthocyanin-containing cells, p-coumaric acid was the best substrate, and caffeic acid and ferulic acid were also activated. With enzyme from anthocyanin-free cells, the lowest Km values were obtained for caffeic acid, while ferulic acid had higher values, and p-coumaric acid was nearly inactive. The enzyme did not separate into isoenzymes during purification. Only on polyacrylamide gels the partially purified enzyme from anthocyanin-containing cells separated into three peaks, and that from anthocyanin-free cells, into only two peaks. This difference is discussed in the context of the lack of activity with p-coumaric acid in anthocyanin-free cells.