In vivo, involved in the biosynthesis of 2-carboxy-6-hydroxyoctahydroindole (Choi) present in the nonribosomal glycopeptides aeruginoside 126A and B. AerD is an unusual prephenate decarboxylase that avoids the typical aromatization of the cyclohexadienol ring of prephenate. AerD catalyzes the protonation at C8 followed by decarboxylation to produce the dihydro-4-hydroxyphenylpyruvate regioisomer A258 (H2HPP A258)(3-(4-hydroxycyclohexa- 1,5-dienyl)-2-oxopropanoic acid), which is able to undergo a nonenzymatic isomerization to produce dihydro-4-hydroxyphenylpyruvate regioisomer A295 (H2HPP A295)(3-(4-hydroxycyclohex-2-enylidene)-2-oxopropanoic acid). H(+) + prephenate = 3-[(4R)-4-hydroxycyclohexa-1,5-dien-1-yl]-2-oxopropanoate + CO2 kcat is 245 min(-1) for decarboxylase activity with prephenate as substrate. Cells lacking this gene are unable to produce aeruginoside 126A and B. Belongs to the prephenate decarboxylase family.