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Two-Component Flavin-Dependent Riboflavin Monooxygenase Degrades Riboflavin in Devosia riboflavina.
- Source :
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Journal of bacteriology [J Bacteriol] 2018 May 24; Vol. 200 (12). Date of Electronic Publication: 2018 May 24 (Print Publication: 2018). - Publication Year :
- 2018
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Abstract
- The actinobacterium Microbacterium maritypicum splits riboflavin (vitamin B <subscript>2</subscript> ) into lumichrome and d-ribose. However, such degradation by other bacteria and the involvement of a two-component flavin-dependent monooxygenase (FMO) in the reaction remain unknown. Here we investigated the mechanism of riboflavin degradation by the riboflavin-assimilating alphaproteobacterium Devosia riboflavina (formerly Pseudomonas riboflavina ). We found that adding riboflavin to bacterial cultures induced riboflavin-degrading activity and a protein of the FMO family that had 67% amino acid identity with the predicted riboflavin hydrolase (RcaE) of M. maritypicum MF109. The D. riboflavina genome clustered genes encoding the predicted FMO, flavin reductase (FR), ribokinase, and flavokinase, and riboflavin induced their expression. This finding suggests that these genes constitute a mechanism for utilizing riboflavin as a carbon source. Recombinant FMO (rFMO) protein of D. riboflavina oxidized riboflavin in the presence of reduced flavin mononucleotide (FMN) provided by recombinant FR (rFR), oxidized FMN and NADH, and produced stoichiometric amounts of lumichrome and d-ribose. Further investigation of the enzymatic properties of D. riboflavina rFMO indicated that rFMO-rFR coupling accompanied O <subscript>2</subscript> consumption and the generation of enzyme-bound hydroperoxy-FMN, which are characteristic of two-component FMOs. These results suggest that D. riboflavina FMO is involved in hydroperoxy-FMN-dependent mechanisms to oxygenize riboflavin and a riboflavin monooxygenase is necessary for the initial step of riboflavin degradation. IMPORTANCE Whether bacteria utilize either a monooxygenase or a hydrolase for riboflavin degradation has remained obscure. The present study found that a novel riboflavin monooxygenase, not riboflavin hydrolase, facilitated this process in D. riboflavina The riboflavin monooxygenase gene was clustered with flavin reductase, flavokinase, and ribokinase genes, and riboflavin induced their expression and riboflavin-degrading activity. The gene cluster is uniquely distributed in Devosia species and actinobacteria, which have exploited an environmental niche by developing adaptive mechanisms for riboflavin utilization.<br /> (Copyright © 2018 American Society for Microbiology.)
- Subjects :
- Alphaproteobacteria genetics
Alphaproteobacteria metabolism
Bacterial Proteins genetics
FMN Reductase genetics
FMN Reductase metabolism
Flavin Mononucleotide metabolism
Flavins metabolism
Mixed Function Oxygenases genetics
Phosphotransferases (Alcohol Group Acceptor) genetics
Phosphotransferases (Alcohol Group Acceptor) metabolism
Alphaproteobacteria enzymology
Bacterial Proteins metabolism
Dinitrocresols metabolism
Mixed Function Oxygenases metabolism
Riboflavin metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 1098-5530
- Volume :
- 200
- Issue :
- 12
- Database :
- MEDLINE
- Journal :
- Journal of bacteriology
- Publication Type :
- Academic Journal
- Accession number :
- 29610214
- Full Text :
- https://doi.org/10.1128/JB.00022-18