Tyrosine decarboxylase activity of Enterococcus mundtii: new insights into phenotypic and genetic aspects.
Few information is available about the tyraminogenic potential of the species Enterococcus mundtii. In this study, two plant-derived strains of E. mundtii were selected and investigated to better understand the phenotypic behaviour and the genetic mechanisms involved in tyramine accumulation. Both the strains accumulated tyramine from the beginning of exponential phase of growth, independently on the addition of tyrosine to the medium. The strains accumulated also 2-phenylethylamine, although with lower efficiency and in greater extent when tyrosine was not added. Accordingly, the tyrosine decarboxylase (tyrDC) gene expression level increased during the exponential phase with tyrosine added, while it remained constant and high without precursor. The genetic organization as well as sequence identity levels of tyrDC and tyrosine permease (tyrP) genes indicated a correlation with those of phylogenetically closer enterococcal species, such as E. faecium, E. hirae and E. durans; however, the gene Na+/H+ antiporter (nhaC) that usually follow tyrP is missing. In addition, BLAST analysis revealed the presence of additional genes encoding for decarboxylase and permease in the genome of several E. mundtii strains. It is speculated the occurrence of a duplication event and the acquisition of different specificity for these enzymes that deserves further investigations.
Department of Biotechnology, University of Verona, Verona, Italy.
Veronica
V
Gatto
Department of Agricultural and Food Sciences, University of Bologna, Cesena, Italy.
Giulia
G
Tabanelli
Interdepartmental Center for Industrial Agri-food Research, University of Bologna, Cesena, Italy.
Chiara
C
Montanari
Department of Biotechnology, University of Verona, Verona, Italy.
Valentina
V
Prodomi
Department of Agricultural and Food Sciences, University of Bologna, Cesena, Italy.
Eleonora
E
Bargossi
Department of Biotechnology, University of Verona, Verona, Italy. sandra.torriani@univr.it.
Sandra
S
Torriani
Department of Agricultural and Food Sciences, University of Bologna, Cesena, Italy.|Interdepartmental Center for Industrial Agri-food Research, University of Bologna, Cesena, Italy.
Fausto
F
Gardini
D016172:DNA Fingerprinting; D016983:Enterococcus / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development; D019143:Evolution, Molecular; D020869:Gene Expression Profiling; D023061:Gene Order; D010627:Phenethylamines / Q000378:metabolism; D019105:Random Amplified Polymorphic DNA Technique; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D014439:Tyramine / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism; D014445:Tyrosine Decarboxylase / Q000032:analysis* / Q000235:genetics*
D010627:Phenethylamines; C029261:phenethylamine; D014443:Tyrosine; D014445:Tyrosine Decarboxylase; D014439:Tyramine