Document Detail

Eukaryotic-type aromatic amino acid decarboxylase from the root colonizer Pseudomonas putida is highly specific for 3,4-dihydroxyphenyl-L-alanine, an allelochemical in rhizosphere.
MedLine Citation:
PMID:  23059975     Owner:  NLM     Status:  Publisher    
Aromatic amino acid decarboxylases (AADCs) are found in various organisms and play distinct physiological roles. AADCs from higher eukaryotes have been well studied because they are involved in the synthesis of biologically important molecules such as neurotransmitters and alkaloids. In contrast, bacterial AADCs have received less attention because of the simplicity in physiology and in target substrate (tyrosine). In the present study, we found that Pseudomonas putida KT2440 possesses an AADC homologue (PP_2552) that is more closely related to eukaryotic enzymes than to bacterial enzymes, and determined the genetic and enzymatic characteristics of the homologue. The purified enzyme converted 3,4-dihydroxyphenyl-L-alanine (DOPA) to dopamine with the Km and kcat values of 0.092 mM and 1.8 s-1, respectively. The enzyme was essentially inactive on other aromatic amino acids such as 5-hydroxy-L-tryptophan, L-phenylalanine, L-tryptophan, and L-tyrosine. The observed strict substrate specificity is distinct from that of any AADCs characterized so far. The proposed name of this enzyme is DOPA decarboxylase (DDC). Expression of the gene was induced by DOPA, as revealed by quantitative RT-PCR analysis. DDC is encoded in a cluster together with a LysR-type transcriptional regulator and a major facilitator superfamily transporter. This genetic organization is conserved among all sequenced P. putida species that inhabit the rhizosphere environment, where DOPA acts as a strong allelochemical. These findings suggest the possible involvement of this enzyme in detoxification of the allelochemical in the rhizosphere, and potential occurrence of a horizontal gene transfer event between the pseudomonad and its host organism.
Takashi Koyanagi; Akira Nakagawa; Haruko Sakurama; Keiko Yamamoto; Naofumi Sakurai; Yukinobu Takagi; Hiromichi Minami; Takane Katayama; Hidehiko Kumagai
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-10-11
Journal Detail:
Title:  Microbiology (Reading, England)     Volume:  -     ISSN:  1465-2080     ISO Abbreviation:  Microbiology (Reading, Engl.)     Publication Date:  2012 Oct 
Date Detail:
Created Date:  2012-10-12     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9430468     Medline TA:  Microbiology     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Ishikawa Prefectural University.
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