ID   CFI_ALLCE               Reviewed;         226 AA.
AC   Q6QHK0; Q66VY8; Q66VY9;
DT   11-SEP-2007, integrated into UniProtKB/Swiss-Prot.
DT   05-JUL-2004, sequence version 1.
DT   03-AUG-2022, entry version 63.
DE   RecName: Full=Chalcone--flavanone isomerase;
DE            Short=Chalcone isomerase;
DE            EC=5.5.1.6;
GN   Name=CHI;
OS   Allium cepa (Onion).
OC   Eukaryota; Viridiplantae; Streptophyta; Embryophyta; Tracheophyta;
OC   Spermatophyta; Magnoliopsida; Liliopsida; Asparagales; Amaryllidaceae;
OC   Allioideae; Allieae; Allium.
OX   NCBI_TaxID=4679;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA / MRNA] (ALLELES B; H AND T).
RC   STRAIN=cv. H6, cv. Serrana, and cv. Texas Early White;
RA   Kim S., Binzel M.L., Yoo K., Pike L.M.;
RT   "Isolation of anthocyanin biosynthesis genes from onion (Allium cepa).";
RL   Submitted (FEB-2004) to the EMBL/GenBank/DDBJ databases.
CC   -!- FUNCTION: Catalyzes the intramolecular cyclization of bicyclic
CC       chalcones into tricyclic (S)-flavanones. Responsible for the
CC       isomerization of 4,2',4',6'-tetrahydroxychalcone (also termed chalcone)
CC       into naringenin (By similarity). {ECO:0000250}.
CC   -!- CATALYTIC ACTIVITY:
CC       Reaction=a chalcone = a flavanone.; EC=5.5.1.6;
CC   -!- PATHWAY: Secondary metabolite biosynthesis; flavonoid biosynthesis.
CC   -!- POLYMORPHISM: There are at least three alleles: H (sequence displayed)
CC       found in cv. H6, B found in cv. Serrana, and T found in cv. Texas Early
CC       White. {ECO:0000269|Ref.1}.
CC   -!- MISCELLANEOUS: Part of the biosynthetic pathway for all classes of
CC       flavonoids, a large class of secondary plant metabolites, many of which
CC       are brightly colored.
CC   -!- SIMILARITY: Belongs to the chalcone isomerase family. {ECO:0000305}.
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DR   EMBL; AY541034; AAS48418.1; -; mRNA.
DR   EMBL; AY700850; AAU11843.1; -; Genomic_DNA.
DR   EMBL; AY700851; AAU11844.1; -; Genomic_DNA.
DR   EMBL; AY700852; AAU11845.1; -; Genomic_DNA.
DR   AlphaFoldDB; Q6QHK0; -.
DR   SMR; Q6QHK0; -.
DR   UniPathway; UPA00154; -.
DR   GO; GO:0045430; F:chalcone isomerase activity; IEA:UniProtKB-EC.
DR   GO; GO:0009813; P:flavonoid biosynthetic process; IEA:UniProtKB-UniPathway.
DR   Gene3D; 1.10.890.20; -; 1.
DR   Gene3D; 3.50.70.10; -; 1.
DR   InterPro; IPR044164; CFI.
DR   InterPro; IPR016087; Chalcone_isomerase.
DR   InterPro; IPR016088; Chalcone_isomerase_3-sand.
DR   InterPro; IPR016089; Chalcone_isomerase_bundle_sf.
DR   InterPro; IPR036298; Chalcone_isomerase_sf.
DR   PANTHER; PTHR28039; PTHR28039; 1.
DR   Pfam; PF02431; Chalcone; 1.
DR   SUPFAM; SSF54626; SSF54626; 1.
PE   2: Evidence at transcript level;
KW   Flavonoid biosynthesis; Isomerase.
FT   CHAIN           1..226
FT                   /note="Chalcone--flavanone isomerase"
FT                   /id="PRO_0000300830"
FT   BINDING         47
FT                   /ligand="substrate"
FT                   /evidence="ECO:0000250"
FT   BINDING         112
FT                   /ligand="substrate"
FT                   /evidence="ECO:0000250"
FT   BINDING         189
FT                   /ligand="substrate"
FT                   /evidence="ECO:0000250"
FT   SITE            105
FT                   /note="Important for catalytic activity"
FT                   /evidence="ECO:0000250"
FT   VARIANT         168
FT                   /note="S -> L (in strain: cv. Serrana and cv. Texas Early
FT                   White)"
FT   VARIANT         170
FT                   /note="S -> P (in strain: cv. Serrana and cv. Texas Early
FT                   White)"
FT   VARIANT         194
FT                   /note="H -> Y (in strain: cv. Texas Early White)"
SQ   SEQUENCE   226 AA;  24172 MW;  291B887F48B852C9 CRC64;
     MEAVTKLDVE GTAFDSVIIP PGSSKTHFLG GAGVRGLEIG GKFIAFTAIG IYLETDSIPF
     LADKWKGKTG EELAGSLDFF RDICTGPFEK FTNVTMILPL TGEQYSEKVT ENCVAYWKAI
     GIYTDAEASA VDKFKQAFKP ESFPPGSSIL FTHTPSGTLK IAFSKDGSVS KDEGVLIENK
     ALTQAVLESI IGEHGVSPAA KLSIASRLSE IMNKVGNVEE KLPVLS