Artículos de revistas
Characterization of the melA Locus for α-Galactosidase in Lactobacillus plantarum
Fecha
2002-11Registro en:
Silvestroni, Aurelio; Connes, Cristelle; Sesma, Fernando Juan Manuel; Savoy, Graciela; Piard, Jean-Christophe; Characterization of the melA Locus for α-Galactosidase in Lactobacillus plantarum; American Society for Microbiology; Applied And Environmental Microbiology; 68; 11; 11-2002; 5464-5471
0099-2240
1098-5336
CONICET Digital
CONICET
Autor
Silvestroni, Aurelio
Connes, Cristelle
Sesma, Fernando Juan Manuel
Savoy, Graciela
Piard, Jean-Christophe
Resumen
Alpha-galactosides are abundant sugars in legumes such as soy. Because of the lack of alpha-galactosidase (alpha-Gal) in the digestive tract, humans are unable to digest these sugars, which consequently induce flatulence. To develop the consumption of the otherwise highly nutritional soy products, the use of exogenous alpha-Gal is promising. In this framework, we characterized the melA gene for alpha-Gal in Lactobacillus plantarum. The melA gene encodes a cytoplasmic 84-kDa protein whose enzymatically active form occurs as oligomers. The melA gene was cloned and expressed in Escherichia coli, yielding an active alpha-Gal. We show that melA is transcribed from its own promoter, yielding a monocistronic mRNA, and that it is regulated at the transcriptional level, i.e., it is induced by melibiose but is not totally repressed by glucose. Post-transcriptional regulation by the carbon source could also occur. Upstream of melA, a putative galactoside transporter, designated RafP, was identified that shows high homology to LacS, the unique transporter for both alpha- and alpha-galactosides in Streptococcus thermophilus. rafP is also expressed as a monocistronic mRNA. Downstream of melA, the lacL and lacM genes were identified that encode a heterodimeric alpha-galactosidase. A putative galM gene identified in the same cluster suggests the presence of a galactose operon. These results indicate that the genes involved in galactoside catabolism are clustered in L. plantarum ATCC 8014. This first genetic characterization of melA and of its putative associated transporter, rafP, in a lactobacillus opens doors to various applications both in the manufacture of soy-derived products and in probiotic and nutraceutical issues.