CHARACTERIZATION OF CATECHOL CATABOLIC GENES FROM RHODOCOCCUS-ERYTHROPOLIS 1CP

The biochemical characterization of the muconate and the chloromuconat e cycloisomerases of the chlorophenol-utilizing Rhodococcus erythropol is strain 1CP previously indicated that efficient chloromuconate conve rsion among the gram-positive bacteria might have evolved independentl y of that among gram-negative bacteria. Based on sequences of the N te rminus and of tryptic peptides of the muconate cycloisomerase, a fragm ent of the corresponding gene has now been amplified and used as a pro be for the cloning of catechol catabolic genes from R. erythropolis. T he clone thus obtained expressed catechol 1,2-dioxygenase, muconate cy cloisomerase, and muconolactone isomerase activities. Sequencing of th e insert on the recombinant plasmid pRER1 revealed that the genes are transcribed in the order catA cafB catC. Open reading frames downstrea m of catC may have a function in carbohydrate metabolism. The predicte d protein sequence of the catechol 1,2-dioxygenase was identical to th e one from Arthrobacter sp. strain mA3 in 59% of the positions. The ch lorocatechol 1,2-dioxygenases and the chloromuconate cycloisomerases o f gram-negative bacteria appear to be more closely related to the cate chol 1,2-dioxygenases and muconate cycloisomerases of the gram-positiv e strains than to the corresponding enzymes of gram-negative bacteria.