Molecular and biochemical analysis of phthalate and terephthalate degradation by Rhodococcus sp. strain DK17.
Alkylbenzene-degrading Rhodococcus sp. strain DK17 is able to utilize phthalate and terephthalate as growth substrates. The genes encoding the transformation of phthalate and terephthalate to protocatechuate are organized as two separate operons, located 6.7kb away from each other. Interestingly, both the phthalate and terephthalate operons are induced in response to terephthalate while expression of the terephthalate genes is undetectable in phthalate-grown cells. In addition to two known plasmids (380-kb pDK1 and 330-kb pDK2), a third megaplasmid (750-kb pDK3) was newly identified in DK17. The phthalate and terephthalate operons are duplicated and are present on both pDK2 and pDK3. RT-PCR experiments, coupled with sequence analysis, suggest that phthalate and terephthalate degradation in DK17 proceeds through oxygenation at carbons 3 and 4 and at carbons 1 and 2 to form 3,4-dihydro-3,4-dihydroxyphthalate and 1,2-dihydro-1,2-dihydroxyterephthalate, respectively. The 3,4-dihydroxyphthalate pathway was further corroborated through colorometric tests. Apparently, the two dihydrodiol metabolites are subsequently dehydrogenated and decarboxylated to form protocatechuate, which is further degraded by a protocatechuate 3,4-dioxygenase as confirmed by a ring-cleavage enzyme assay.
Choi
Ki Young
KY
Department of Biology, Yonsei University, Seoul, Republic of Korea.
Kim
Dockyu
D
Sul
Woo Jun
WJ
Chae
Jong-Chan
JC
Zylstra
Gerben J
GJ
Kim
Young Min
YM
Kim
Eungbin
E
D001673:Biodegradation, Environmental; D020440:Gene Duplication; D015964:Gene Expression Regulation, Bacterial; D023061:Gene Order; D009876:Operon; D010795:Phthalic Acids / Q000378:metabolism*; D011520:Protocatechuate-3,4-Dioxygenase / Q000378:metabolism; D012240:Rhodococcus / Q000235:genetics / Q000378:metabolism*
D010795:Phthalic Acids; C032279:phthalic acid; C011363:terephthalic acid; D011520:Protocatechuate-3,4-Dioxygenase