Tyramine biosynthesis in Enterococcus durans is transcriptionally regulated by the extracellular pH and tyrosine concentration.
Bottom Line: One of the most abundant and frequent biogenic amines found in fermented foods is tyramine, which is produced by the decarboxylation of tyrosine.The gene coding for the tyrosine decarboxylase (tdcA) and that coding for the tyrosine-tyramine antiporter (tyrP) form an operon transcribed from the promoter P(tdcA), the expression of which is regulated by the extracellular pH and tyrosine concentration.Quantification of gene expression during the log phase of growth showed high concentrations of tyrosine and acidic pH conditions to induce tdcA-tyrP polycistronic messenger transcription.
Affiliation: Instituto de Productos Lácteos de Asturias (IPLA), Consejo Superior de Investigaciones Científicas (CSIC), Carretera de Infiesto s/n, 33300 Villaviciosa, Asturias, Spain.Show MeSH
Related in: MedlinePlus
Mentions: To determine the expression profile of tdcA and tyrP, according to previously obtained physiological data (Fernández et al., 2007), Northern blot experiments were performed with RNA obtained from E. durans IPLA655 cultures grown at pH 4.9 and 7.5 in presence and absence of 10 mM tyrosine. The expression of tdcA and tyrP required a low pH and the presence of tyrosine, which are conditions previously shown to induce tyramine synthesis (Fernández et al., 2007) (Fig. 1). Only under these conditions the tdcA specific probe revealed a 1.9 kb and a 3.6 kb band (Fig. 1A). The larger fragment was also detected under the same conditions after hybridization with the tyrP probe (Fig. 1B), suggesting the existence of a polycistronic mRNA molecule covering both genes. No monocistronic band was detected with the tyrP probe. These results indicate that tdcA may be transcribed from its own promoter as a monocistronic mRNA, or with tyrP as part of a polycistronic mRNA tdcA‐tyrP. However, tyrP did not seem to have its own promoter; transcription was dependent on the tdcA promoter.
Affiliation: Instituto de Productos Lácteos de Asturias (IPLA), Consejo Superior de Investigaciones Científicas (CSIC), Carretera de Infiesto s/n, 33300 Villaviciosa, Asturias, Spain.