title: First evidence of a membrane-bound, tyramine and beta-phenylethylamine producing, tyrosine decarboxylase in Enterococcus faecalis: a two-dimensional electrophoresis proteomic study.
abstract: The soluble and membrane proteome of a tyramine producing Enterococcus faecalis, isolated from an Italian goat cheese, was investigated. A detailed analysis revealed that this strain also produces small amounts of beta-phenylethylamine. Kinetics of tyramine and beta-phenylethylamine accumulation, evaluated in tyrosine plus phenylalanine-enriched cultures (stimulated condition), suggest that the same enzyme, the tyrosine decarboxylase (TDC), catalyzes both tyrosine and phenylalanine decarboxylation: tyrosine was recognized as the first substrate and completely converted into tyramine (100% yield) while phenylalanine was decarboxylated to beta-phenylethylamine (10% yield) only when tyrosine was completely depleted. The presence of an aspecific aromatic amino acid decarboxylase is a common feature in eukaryotes, but in bacteria only indirect evidences of a phenylalanine decarboxylating TDC have been presented so far. Comparative proteomic investigations, performed by 2-DE and MALDI-TOF/TOF MS, on bacteria grown in conditions stimulating tyramine and beta-phenylethylamine biosynthesis and in control conditions revealed 49 differentially expressed proteins. Except for aromatic amino acid biosynthetic enzymes, no significant down-regulation of the central metabolic pathways was observed in stimulated conditions, suggesting that tyrosine decarboxylation does not compete with the other energy-supplying routes. The most interesting finding is a membrane-bound TDC highly over-expressed during amine production. This is the first evidence of a true membrane-bound TDC, longly suspected in bacteria on the basis of the gene sequence.
authors.affiliation: Dipartimento di Biologia Animale e dell'Uomo, University of Torino, Via Accademia Albertina 13, Turin, Italy. enrica.pessione@unito.it
authors.forename: Enrica
authors.initials: E
authors.lastname: Pessione
authors.forename: Alessandro
authors.initials: A
authors.lastname: Pessione
authors.forename: Cristina
authors.initials: C
authors.lastname: Lamberti
authors.forename: Daniel Jean
authors.initials: DJ
authors.lastname: Coïsson
authors.forename: Kathrin
authors.initials: K
authors.lastname: Riedel
authors.forename: Roberto
authors.initials: R
authors.lastname: Mazzoli
authors.forename: Silvia
authors.initials: S
authors.lastname: Bonetta
authors.forename: Leo
authors.initials: L
authors.lastname: Eberl
authors.forename: Carlo
authors.initials: C
authors.lastname: Giunta
mesh_terms: D001679:Biogenic Amines / Q000378:metabolism; D002611:Cheese / Q000382:microbiology; D003627:Data Interpretation, Statistical; D015180:Electrophoresis, Gel, Two-Dimensional; D013293:Enterococcus faecalis / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D005516:Food Microbiology; D007700:Kinetics; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D010627:Phenethylamines / Q000378:metabolism*; D040901:Proteomics; D014439:Tyramine / Q000378:metabolism*; D014445:Tyrosine Decarboxylase / Q000235:genetics / Q000378:metabolism*
chemical_list: D001679:Biogenic Amines; D008565:Membrane Proteins; D010627:Phenethylamines; C029261:phenethylamine; D014445:Tyrosine Decarboxylase; D014439:Tyramine