Anthocyanin accumulation and PAL activity in a suspension culture of Daucus carota L.. Inhibition by L-alpha-aminooxy-beta-phenylpropionic acid and t-cinnamic acid

• Published in: Planta Vol. 149; no. 3; pp. 283 - 287
• Main Authors: Noe, W, Langebartels, C, Seitz, H.U
• Format: Journal Article
• Language: English
• Published: Germany Springer-Verlag 01-08-1980
• Subjects: Amino acids; Ammonia; Biosynthesis; carrots; Cell growth; Cell lines; Chemical suspensions; Cultured cells; Enzymes; Hypocotyls; Inoculation
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/BF00384567

Cells of Daucus carota grown in a liquid medium produced large amounts of cyanidin as the only flavonoid aglycon. After inoculation in fresh medium a maximum activity of phenylalanine ammonia lyase (PAL; EC 4.3.1.5) was observed within 24 h. L-α-aminooxy-β-phenylpropionic acid (L-AOPP), thought to be a competitive inhibitor of PAL, inhibited cyanidin accumulation up to 80%. In order to study the regulatory role of PAL, the effects of L-AOPP and t-cinnamic acid, the product of the deamination of phenylalanine, were investigated. Cinnamic acid, applied in vivo (10-4 M), was not able to compensate for the inhibition of cyanidin production caused by L-AOPP (10-4 M) in the same sample. Carrot cells treated with L-AOPP exhibited a "superinduction" of PAL already described for gherkin hypocotyls (Amrhein and Gerhardt 1979). This effect was not influenced by t-cinnamic acid. L-AOPP seems to be a very specific inhibitor since it affected neither growth nor soluble protein content, whereas t-cinnamic acid inhibited both. Investigations on the content of soluble amino acids in L-AOPP-treated cells revealed a specific accumulation of soluble phenylalanine, whereas treatment with t-cinnamic acid led to an increase of amino acids in general, thus indicating that the latter compound has a rather unspecific effect on cellular metabolism. In vitro studies with PAL isolated from Daucus carota revealed that L-AOPP inhibited the enzyme at very low doses (KI = 2.4·10-9), whereas t-cinnamic acid, by comparison, affected the enzyme at high concentrations (KI = 1.8·10-4).