Document Detail

Involvement of the detoxifying enzyme lactoylglutathione lyase in Streptococcus mutans aciduricity.
MedLine Citation:
PMID:  17720789     Owner:  NLM     Status:  MEDLINE    
Streptococcus mutans, a normal inhabitant of dental plaque, is considered a primary etiological agent of dental caries. Its main virulence factors are acidogenicity and aciduricity, the abilities to produce acid and to survive and grow at low pH, respectively. Metabolic processes are finely regulated following acid exposure in S. mutans. Proteome analysis of S. mutans demonstrated that lactoylglutathione lyase (LGL) was up-regulated during acid challenge. The LGL enzyme catalyzes the conversion of toxic methylglyoxal, derived from glycolysis, to S-D-lactoylglutathione. Methylglyoxal inhibits the growth of cells in all types of organisms. The current study aimed to investigate the relationship between LGL and aciduricity and acidogenicity in S. mutans. An S. mutans isogenic mutant defective in lgl (LGLKO) was created, and its growth kinetics were characterized. Insertional inactivation of lgl resulted in an acid-sensitive phenotype. However, the glycolytic rate at pH 5.0 was greater for LGLKO than for S. mutans UA159 wild-type cells. LGL was involved in the detoxification of methylglyoxal, illustrated by the absence of enzyme activity in LGLKO and the hypersensitivity of LGLKO to methylglyoxal, compared with UA159 (MIC of 3.9 and 15.6 mM, respectively). Transcriptional analysis of lgl conducted by quantitative real-time PCR revealed that lgl was up-regulated (approximately sevenfold) during the exponential growth phase compared with that in the stationary growth phase. Gene expression studies conducted at low pH demonstrated that lgl was induced during acidic growth (approximately 3.5-fold) and following acid adaptation (approximately 2-fold). This study demonstrates that in S. mutans, LGL functions in the detoxification of methylglyoxal, resulting in increased aciduricity.
Bryan Korithoski; Céline M Lévesque; Dennis G Cvitkovitch
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Publication Detail:
Type:  Journal Article     Date:  2007-08-24
Journal Detail:
Title:  Journal of bacteriology     Volume:  189     ISSN:  0021-9193     ISO Abbreviation:  J. Bacteriol.     Publication Date:  2007 Nov 
Date Detail:
Created Date:  2007-10-18     Completed Date:  2008-01-08     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  2985120R     Medline TA:  J Bacteriol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  7586-92     Citation Subset:  IM    
Dental Research Institute, University of Toronto, 124 Edward St., Toronto, Ontario, Canada M5G 1G6.
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MeSH Terms
Base Sequence
DNA Primers
Gene Expression Regulation, Bacterial
Gene Expression Regulation, Enzymologic
Hydrogen-Ion Concentration
Lactoylglutathione Lyase / deficiency,  genetics,  metabolism*
Pyruvaldehyde / toxicity*
Streptococcus mutans / drug effects,  enzymology*,  genetics
Reg. No./Substance:
0/DNA Primers; 78-98-8/Pyruvaldehyde; EC Lyase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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