Possible regulatory role for nonaromatic carbon sources in styrene degradation by Pseudomonas putida CA-3

Abstract

Styrene metabolism in styrene-degrading Pseudomonas putida CA-3 cells has been shown to proceed via styrene oxide, phenylacetaldehyde, and phenylacetic acid. The initial step in styrene degradation by strain CA-3 is oxygen-dependent epoxidation of styrene to styrene oxide, which is subsequently isomerized to phenylacetaldehyde. Phenylacetaldehyde is then oxidized to phenylacetic acid. Styrene, styrene oxide, and phenylacetaldehyde induce the enzymes involved in the degradation of styrene to phenylacetic acid by P. putida CA-3. Phenylacetic acid-induced cells do not oxidize styrene or styrene oxide. Thus, styrene degradation by P. putida CA-3 can be subdivided further into an upper pathway which consists of styrene, styrene oxide, and phenylacetaldehyde and a lower pathway which begins with phenylacetic acid. Studies of the repression of styrene degradation by P. putida CA-3 show that glucose has no effect on the activity of styrene-degrading enzymes. However, both glutamate and citrate repress styrene degradation and phenylacetic acid degradation, showing a common control mechanism on upper pathway and lower pathway intermediates.