Induction of 4-hydroxycinnamate decarboxylase in Klebsiella oxytoca cells exposed to substrates and non-substrate 4-hydroxycinnamate analogs

The 4-hydroxycinnamate decarboxylase (4-HCD)-inducing activity of several substrate analogs towardKlebsiella oxytoca was investigated. Four E-cinnamateclass compounds, E-4-hydroxycinnamic acid (1), caffeic acid (2), ferulic acid (3) and E-2,4-dihydroxycinnamic acid (4), all of which were accepted as substrates, all of which were accepted as substrates of 4-HCD, enable K. oxytoca cells to induce the decarboxylase at a 2.0 mM concentration, while five non-substrate compounds of the E-cinnamate class so far tested were completely in active. However, 6-hydroxy-2-naphthoic acid (11) and 7-hydroxycoumarin 3-carboxyIic acid (14), both of which are non-cinnamate-class analogs of the substrate, acted as strong 4-HCD inducers, even at a 0.5 mM concentration. The 4-HCD-inducing activities of compounds 11 and 14 at 0.5 mM were 10-12-fold higher than that of substrate 1. Compound 11 maintained its 4-HCD-inducing activity toward cultured cells through