Characterization of p-hydroxybenzaldehyde dehydrogenase, the final enzyme of p-hydroxybenzoic acid biosynthesis in hairy roots of Daucus carota

Hairy root cultures of Daucus carota respond to methyl-jasmonate treatment with enhanced accumulation of p-hydroxybenzoic acid. The final C1-side chain of this compound is shaped by p-hydroxybenzaldehyde dehydrogenase (HBD) that catalyzes the formation of p-hydroxybenzoic acid from p-hydroxybenzaldehyde in the presence of NAD+. HBD was biochemically characterized from cell-free hairy root extracts of D. carota. The preferred substrate for HBD was p-hydroxybenzaldehyde. The apparent Km values were 54.8 and 74.4 μM for p-hydroxybenzaldehyde and NAD+, respectively. Divalent metal cations did not significantly affect enzyme activity.