The degradation of l-histidine, imidazolyl-l-lactate and imidazolylpropionate by Pseudomonas testosteroni

Abstract

1. Imidazol-5-ylpropionate and imidazol-5-yl-lactate are degraded by Pseudomonas testosteroni via inducible pathways. 2. Growth on either compound as the sole source of carbon results in the induction of the enzymes for histidine catabolism. 3. The pathway of histidine degradation in this organism, a non-fluorescent Pseudomonad, is shown to be the same as that operating in Pseudomonas fluorescens and Pseudomonas putida. It consists of the successive formation of urocanate, imidazol-4-on-5-ylpropionate, N-formimino-l-glutamate, N-formyl-l-glutamate and glutamate. 4. Whole cells of P. testosteroni accumulate urocanate in the reaction mixture when incubated with imidazolylpropionate, but only after an adaptive lag period which is removed by previous growth on imidazolylpropionate as the source of carbon. 5. Imidazolyl-lactate is oxidized to imidazolylpyruvate, which then gives rise to histidine by specific transamination with l-glutamate. 6. Cells grown on histidine, urocanate or imidazolylpropionate are also able to degrade imidazolyllactate. 7. Mutants lacking urocanase are unable to grow on imidazolylpropionate, imidazolyl-lactate, histidine or urocanate. One with impaired histidase activity cannot utilize histidine or imidazolyl-lactate, but grows normally on imidazolylpropionate or urocanate. A mutant unable to grow on imidazolylpropionate is indistinguishable from the wild-type with respect to growth on histidine, imidazolyl-lactate or urocanate. 8. Thus it is established that imidazolyl-lactate is metabolized via histidine whereas imidazolylpropionate enters the histidine degradation pathway after conversion into urocanate.

Binding of the IclR-type regulator HutR in the histidine utilization (hut) gene cluster of the human pathogen Corynebacterium resistens DSM 45100

“…Very recently, the complete genome sequence of C. resistens DSM 45100 has been determined to delineate the putative lifestyle of this opportunistic pathogen on the human body (Schröder et al, 2012). The protein products of orthologous genes catalyze the four-step conversion of L-histidine to L-glutamate (Coote & Hassall, 1973). 1).…”

“…1). The protein products of orthologous genes catalyze the four-step conversion of L-histidine to L-glutamate (Coote & Hassall, 1973). The presence of this pathway in C. resistens is remarkable, as this species probably colonizes the fatty and histidine-rich inguinal and perineal regions of the human body and thus lives in close proximity to the female genital tract (Schröder et al, 2012).…”

Genetic Analysis of the Histidine Utilization (hut) Genes in Pseudomonas fluorescens SBW25

“…In bacteria, catabolism of histidine occurs via either a four or a five-step enzymatic pathway (Coote and Hassall 1973a;Magasanik 1978). The first three steps, from histidine to urocanate, to imidazolone propionate (IPA), to formiminoglutamate (FIGLU), are catalyzed by the gene products of hutH, hutU, and hutI, respectively, and are common to both the four-step and the five-step pathways (outlined in Figure 1A).…”

Organization and multiple regulation of histidine utilization genes in Pseudomonas putida

“…The histidine degradation pathway in Pseudomonas species consists of five reactions (8,16), while four steps are required in most other organisms which have been studied, e.g., Salmonella typhimurium (18), Klebsiella aerogenes (17), Bacillus subtilis (6), and mammalian species (26). The enzymes and their genes required by Pseudomonas putida for the conversion of histidine to glutamate plus formate and ammonia are: histidase (hutH), urocanase (hutU), imidazolone propionate hydrolase (IPAase) (hutl), formiminoglutamate iminohydrolase (FIGLUase) (hutF), and formylglutamate amidohydrolase (FGase) (hutG).…”