title: A directed-overflow and damage-control N-glycosidase in riboflavin biosynthesis.
abstract: Plants and bacteria synthesize the essential human micronutrient riboflavin (vitamin B2) via the same multi-step pathway. The early intermediates of this pathway are notoriously reactive and may be overproduced in vivo because riboflavin biosynthesis enzymes lack feedback controls. In the present paper, we demonstrate disposal of riboflavin intermediates by COG3236 (DUF1768), a protein of previously unknown function that is fused to two different riboflavin pathway enzymes in plants and bacteria (RIBR and RibA respectively). We present cheminformatic, biochemical, genetic and genomic evidence to show that: (i) plant and bacterial COG3236 proteins cleave the N-glycosidic bond of the first two intermediates of riboflavin biosynthesis, yielding relatively innocuous products; (ii) certain COG3236 proteins are in a multi-enzyme riboflavin biosynthesis complex that gives them privileged access to riboflavin intermediates; and (iii) COG3236 action in Arabidopsis thaliana and Escherichia coli helps maintain flavin levels. COG3236 proteins thus illustrate two emerging principles in chemical biology: directed overflow metabolism, in which excess flux is diverted out of a pathway, and the pre-emption of damage from reactive metabolites.
authors.affiliation: *Horticultural Sciences Department, University of Florida, Gainesville, FL 32611, U.S.A.
authors.forename: Océane
authors.initials: O
authors.lastname: Frelin
authors.affiliation: †Food Science and Human Nutrition Department, University of Florida, Gainesville, FL 32611, U.S.A.
authors.forename: Lili
authors.initials: L
authors.lastname: Huang
authors.affiliation: *Horticultural Sciences Department, University of Florida, Gainesville, FL 32611, U.S.A.
authors.forename: Ghulam
authors.initials: G
authors.lastname: Hasnain
authors.affiliation: ‡Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL 60208, U.S.A.
authors.forename: James G
authors.initials: JG
authors.lastname: Jeffryes
authors.affiliation: *Horticultural Sciences Department, University of Florida, Gainesville, FL 32611, U.S.A.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ziemak
authors.affiliation: ║AMRIS Facility, McKnight Brain Institute, University of Florida, Gainesville, FL 32611, U.S.A.
authors.forename: James R
authors.initials: JR
authors.lastname: Rocca
authors.affiliation: ¶Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32611, U.S.A.
authors.forename: Bing
authors.initials: B
authors.lastname: Wang
authors.affiliation: **Institute of Biological Chemistry, Washington State University, Pullman, WA 99164, U.S.A.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Rice
authors.affiliation: **Institute of Biological Chemistry, Washington State University, Pullman, WA 99164, U.S.A.
authors.forename: Sanja
authors.initials: S
authors.lastname: Roje
authors.affiliation: **Institute of Biological Chemistry, Washington State University, Pullman, WA 99164, U.S.A.
authors.forename: Svetlana N
authors.initials: SN
authors.lastname: Yurgel
authors.affiliation: †Food Science and Human Nutrition Department, University of Florida, Gainesville, FL 32611, U.S.A.
authors.forename: Jesse F
authors.initials: JF
authors.lastname: Gregory
authors.affiliation: ¶Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32611, U.S.A.
authors.forename: Arthur S
authors.initials: AS
authors.lastname: Edison
authors.affiliation: §Mathematics and Computer Science Division, Argonne National Laboratory, Argonne, IL 60439, U.S.A.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Henry
authors.affiliation: ‡‡Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, U.S.A.
authors.forename: Valérie
authors.initials: V
authors.lastname: de Crécy-Lagard
authors.affiliation: *Horticultural Sciences Department, University of Florida, Gainesville, FL 32611, U.S.A.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Hanson
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D018506:Gene Expression Regulation, Plant; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D015416:Maillard Reaction; D009699:N-Glycosyl Hydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012256:Riboflavin / Q000096:biosynthesis*; D041261:Vibrio vulnificus / Q000235:genetics / Q000378:metabolism; D003313:Zea mays / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D007527:Isoenzymes; D010940:Plant Proteins; D009699:N-Glycosyl Hydrolases; D012256:Riboflavin