AC   MF_00180;
DC   Protein; auto
TR   HAMAP; MF_00180; -; 1; level=0
XX
Names: RibB
XX
ID   RIBB
DE   RecName: Full=3,4-dihydroxy-2-butanone 4-phosphate synthase;
DE            Short=DHBP synthase;
DE            EC=4.1.99.12;
GN   Name=ribB;
XX
CC   -!- FUNCTION: Catalyzes the conversion of D-ribulose 5-phosphate to formate
CC       and 3,4-dihydroxy-2-butanone 4-phosphate.
CC   -!- CATALYTIC ACTIVITY:
CC       Reaction=D-ribulose 5-phosphate = (2S)-2-hydroxy-3-oxobutyl phosphate +
CC         formate + H(+); Xref=Rhea:RHEA:18457, ChEBI:CHEBI:15378,
CC         ChEBI:CHEBI:15740, ChEBI:CHEBI:58121, ChEBI:CHEBI:58830;
CC         EC=4.1.99.12;
CC   -!- COFACTOR:
CC       Name=Mg(2+); Xref=ChEBI:CHEBI:18420;
CC       Name=Mn(2+); Xref=ChEBI:CHEBI:29035;
CC       Note=Binds 2 divalent metal cations per subunit. Magnesium or
CC       manganese.;
CC   -!- PATHWAY: Cofactor biosynthesis; riboflavin biosynthesis; 2-hydroxy-3-
CC       oxobutyl phosphate from D-ribulose 5-phosphate: step 1/1.
CC   -!- SUBUNIT: Homodimer.
CC   -!- SIMILARITY: Belongs to the DHBP synthase family.
XX
DR   Pfam; PF00926; DHBP_synthase; 1; trigger=no
DR   NCBIfam; TIGR00506; RibB; 1; trigger=no
XX
KW   Lyase
KW   Magnesium
KW   Manganese
KW   Metal-binding
KW   Riboflavin biosynthesis
XX
GO   GO:0000287; F:magnesium ion binding
GO   GO:0008686; F:3,4-dihydroxy-2-butanone-4-phosphate synthase activity
GO   GO:0030145; F:manganese ion binding
GO   GO:0009231; P:riboflavin biosynthetic process
XX
FT   From: RIBB_METJA (Q60364)
FT   BINDING         25..26
FT                   /ligand="D-ribulose 5-phosphate"
FT                   /ligand_id="ChEBI:CHEBI:58121"
FT   Condition: R-E
FT   BINDING         161..165
FT                   /ligand="D-ribulose 5-phosphate"
FT                   /ligand_id="ChEBI:CHEBI:58121"
FT   Condition: R-x-x-[HQ]-T
FT   BINDING         26
FT                   /ligand="Mg(2+)"
FT                   /ligand_id="ChEBI:CHEBI:18420"
FT                   /ligand_label="1"
FT   Condition: E
FT   BINDING         26
FT                   /ligand="Mg(2+)"
FT                   /ligand_id="ChEBI:CHEBI:18420"
FT                   /ligand_label="2"
FT   Condition: E
FT   BINDING         164
FT                   /ligand="Mg(2+)"
FT                   /ligand_id="ChEBI:CHEBI:18420"
FT                   /ligand_label="2"
FT   Condition: H
FT   BINDING         30
FT                   /ligand="D-ribulose 5-phosphate"
FT                   /ligand_id="ChEBI:CHEBI:58121"
FT   Condition: D
FT   SITE            147
FT                   /note="Essential for catalytic activity"
FT   Condition: H
FT   SITE            185
FT                   /note="Essential for catalytic activity"
FT   Condition: E
XX
Size: 200-247;
Related: MF_01283!;
Template: P0A7J0; Q60364;
Scope:
 Bacteria
 Archaea
Fusion:
 Nter: None
 Cter: <ribA-like>
Duplicate: None
Plasmid: in RALN1
Comments: RibA and RibB are fused in some organisms (see MF_01283 for bifunctional RibBA).
 Some ribB are followed by a ribA-like domain, which does not seem to code for GTP
 cyclohydrolase II activity because it lacks all the residues important for activity.
XX
# Revision 1.28 2023/11/28
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