Genetic organization and characteristics of the 3-(3-hydroxyphenyl)propionic acid degradation pathway of Comamonas testosteroni TA441

Comamonas testosteroni TA441 degrades 3-(3-hydroxyphenyl)propionate (3HPP) via the meta pathway. A gene cluster required for degradation of 3HPP was c loned from strain TA441 and sequenced, The genes encoding six catabolic enz ymes, a flavin-type hydroxylase (mhpA), extradiol dioxygenase (mhpB), 2-ket o-4-pentenoate hydratase (mhpD),acetaldehyde dehydrogenase (acylating) (mhp F), 4-hydroxy-2-ketovalerate aldolase (mhpE) and the meta cleavage compound hydrolase (mhpC), were found in this cluster, encoded in this order. mhpD and mhpF were separated by two genes, orf4 and orf5, which were not necessa ry for growth on 3HPP. The gene mhpR, encoding a putative transcriptional a ctivator of the IcIR family, was located adjacent to mhpA in the opposite o rientation. Disruption of the mhpB or mhpR genes affected growth on 3HPP or trans-3-hydroxycinnamate. The mhpB and mhpC gene products showed high spec ificity for 3-(2,3-dihydroxyphenyl)propionate (DHPP) and the meta cleavage compound produced from DHPP, respectively.