Title
Cloning, sequence analysis, and characterization of the genes involved in isoprimeverose metabolism in Lactobacillus pentosus
Author
Chaillou, S.
Lokman, B.C.
Leer, R.J.
Posthuma, C.
Postma, P.W.
Pouwels, P.H.
Publication year
1998
Abstract
Two genes, xylP and xylQ, from the xylose regulon of Lactobacillus pentosus were cloned and sequenced. Together with the repressor gene of the regulon, xylR, the xylPQ genes form an operon which is inducible by xylose and which is transcribed from a promoter located 145 bp upstream of xylP. A putative xylR binding site (xylO) and a cre-like element, mediating CcpA- dependent catabolite repression, were found in the promoter region. L. pentosus mutants in which both xylP and xylQ (LPE1) or only xylQ (LPE2) was inactivated retained the ability to ferment xylose but were impaired in their ability to ferment isoprimeverose (α-D-xylopyranosyl, (1,6)-D- glucopyranose). Disruption of xylQ resulted specifically in the loss of a membrane-associated α-xylosidase activity when LPE1 or LPE2 cells were grown on xylose. In the membrane fraction of wild-type bacteria α-xylosidase could catalyze the hydrolysis of isoprimeverose and p-nitrophenyl-α-D- xylopyranoside with apparent K(m) and V(max) values of 0.2 mM and 446 nmol/min/mg of protein, and 1.3 mM and 54 nmol/min/mg of protein, respectively. The enzyme could also hydrolyze the α-xylosidic linkage in xyloglucan oligosaccharides, but neither methyl-α-D-xylopyranoside nor α- glucosides were substrates. Glucose repressed the synthesis of α-xylosidase fivefold, and 80% of this repression was released in an L. pentosus ΔccpA mutant. The α-xylosidase gene was also expressed in the absence of xylose when xylR was disrupted. Chemicals/CAS: alpha-D-xylosidase, EC 3.2.1.-; Bacterial Proteins; Carrier Proteins; Disaccharides; Glycosides; isoprimeverose cation symporter, Lactobacillus; isoprimeverose, 534-98-5; Symporters; Xylose; Xylosidases, EC 3.2.1.-
Subject
disaccharide
article
bacterial gene
bacterial metabolism
carbohydrate metabolism
fermentation
gene control
gene expression regulation
lactobacillus
molecular cloning
nonhuman
nucleotide sequence
priority journal
regulon
repressor gene
Amino Acid Sequence
Bacterial Proteins
Base Sequence
Carrier Proteins
Cell Compartmentation
Cloning, Molecular
Disaccharides
Genes, Bacterial
Glycosides
Lactobacillus
Molecular Sequence Data
Operon
Sequence Analysis, DNA
Sequence Homology, Amino Acid
Substrate Specificity
Symporters
Xylose
Xylosidases
Bacteria (microorganisms)
Lactobacillus pentosus
Posibacteria
Prokaryota
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TNO identifier
234452
ISSN
0021-9193
Source
Journal of Bacteriology, 180 (9), 2312-2320
Document type
article