A gene cluster involved in degradation of substituted salicylates via ortho cleavage in Pseudomonas sp. strain MT1 encodes enzymes specifically adapted for transformation of 4-methylcatechol and 3-methylmuconate.
Pseudomonas sp. strain MT1 has recently been reported to degrade 4- and 5-chlorosalicylate by a pathway assumed to consist of a patchwork of reactions comprising enzymes of the 3-oxoadipate pathway. Genes encoding the initial steps in the degradation of salicylate and substituted derivatives were now localized and sequenced. One of the gene clusters characterized (sal) showed a novel gene arrangement, with salA, encoding a salicylate 1-hydroxylase, being clustered with salCD genes, encoding muconate cycloisomerase and catechol 1,2-dioxygenase, respectively, and was expressed during growth on salicylate and chlorosalicylate. A second gene cluster (cat), exhibiting the typical catRBCA arrangement of genes of the catechol branch of the 3-oxoadipate pathway in Pseudomonas strains, was expressed during growth on salicylate. Despite their high sequence similarities with isoenzymes encoded by the cat gene cluster, the catechol 1,2-dioxygenase and muconate cycloisomerase encoded by the sal cluster showed unusual kinetic properties. Enzymes were adapted for turnover of 4-chlorocatechol and 3-chloromuconate; however, 4-methylcatechol and 3-methylmuconate were identified as the preferred substrates. Investigation of the substrate spectrum identified 4- and 5-methylsalicylate as growth substrates, which were effectively converted by enzymes of the sal cluster into 4-methylmuconolactone, followed by isomerization to 3-methylmuconolactone. The function of the sal gene cluster is therefore to channel both chlorosubstituted and methylsubstituted salicylates into a catechol ortho cleavage pathway, followed by dismantling of the formed substituted muconolactones through specific pathways.
Cámara
Beatriz
B
Division of Microbiology, HZI-Helmholtz Zentrum für Infektionsforschung, Inhoffenstrasse 7, D-38124 Braunschweig, Germany.
Bielecki
Piotr
P
Kaminski
Filip
F
dos Santos
Vitor Martins
VM
Plumeier
Iris
I
Nikodem
Patricia
P
Pieper
Dietmar H
DH
D001483:Base Sequence; D050548:Catechol 1,2-Dioxygenase / Q000378:metabolism; D002396:Catechols / Q000378:metabolism*; D019753:Intramolecular Lyases / Q000302:isolation & purification / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000302:isolation & purification; D008969:Molecular Sequence Data; D005810:Multigene Family; D011549:Pseudomonas / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012459:Salicylates / Q000378:metabolism*; D013011:Sorbic Acid / Q000031:analogs & derivatives / Q000378:metabolism
D002396:Catechols; D012459:Salicylates; C018599:4-methylcatechol; C005939:muconic acid; D006899:Mixed Function Oxygenases; D050548:Catechol 1,2-Dioxygenase; C022619:salicylate 1-monooxygenase; D019753:Intramolecular Lyases; C021811:muconate cycloisomerase; D013011:Sorbic Acid