ID   BKT_PROBT               Reviewed;         387 AA.
AC   G3F5K2;
DT   07-APR-2021, integrated into UniProtKB/Swiss-Prot.
DT   16-NOV-2011, sequence version 1.
DT   25-MAY-2022, entry version 22.
DE   RecName: Full=Beta-carotene 4-ketolase {ECO:0000303|PubMed:22526507};
DE            Short=PbBKT {ECO:0000303|PubMed:22526507};
DE            EC=1.14.99.63 {ECO:0000269|PubMed:22526507};
GN   Name=BKT {ECO:0000303|PubMed:22526507};
OS   Protosiphon botryoides (Green alga).
OC   Eukaryota; Viridiplantae; Chlorophyta; core chlorophytes; Chlorophyceae;
OC   Protosiphonales; Protosiphonaceae; Protosiphon.
OX   NCBI_TaxID=44656;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [MRNA], FUNCTION, AND CATALYTIC ACTIVITY.
RX   PubMed=22526507; DOI=10.1007/s00425-012-1654-6;
RA   Huang J., Zhong Y., Sandmann G., Liu J., Chen F.;
RT   "Cloning and selection of carotenoid ketolase genes for the engineering of
RT   high-yield astaxanthin in plants.";
RL   Planta 236:691-699(2012).
CC   -!- FUNCTION: Involved in the biosynthesis of ketocarotenoids which are
CC       powerful anti-oxidative molecules (PubMed:22526507). Catalyzes the
CC       conversion of beta-carotene to canthaxanthin via echinenone
CC       (PubMed:22526507). {ECO:0000269|PubMed:22526507}.
CC   -!- CATALYTIC ACTIVITY:
CC       Reaction=2 AH2 + echinenone + 2 O2 = 2 A + canthaxanthin + 3 H2O;
CC         Xref=Rhea:RHEA:55664, ChEBI:CHEBI:3362, ChEBI:CHEBI:4746,
CC         ChEBI:CHEBI:13193, ChEBI:CHEBI:15377, ChEBI:CHEBI:15379,
CC         ChEBI:CHEBI:17499; EC=1.14.99.63;
CC         Evidence={ECO:0000269|PubMed:22526507};
CC       PhysiologicalDirection=left-to-right; Xref=Rhea:RHEA:55665;
CC         Evidence={ECO:0000269|PubMed:22526507};
CC   -!- CATALYTIC ACTIVITY:
CC       Reaction=2 AH2 + all-trans-beta-carotene + 2 O2 = 2 A + echinenone + 3
CC         H2O; Xref=Rhea:RHEA:55660, ChEBI:CHEBI:4746, ChEBI:CHEBI:13193,
CC         ChEBI:CHEBI:15377, ChEBI:CHEBI:15379, ChEBI:CHEBI:17499,
CC         ChEBI:CHEBI:17579; EC=1.14.99.63;
CC         Evidence={ECO:0000269|PubMed:22526507};
CC       PhysiologicalDirection=left-to-right; Xref=Rhea:RHEA:55661;
CC         Evidence={ECO:0000269|PubMed:22526507};
CC   -!- PATHWAY: Carotenoid biosynthesis. {ECO:0000305}.
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DR   EMBL; JF451849; AEM45621.1; -; mRNA.
DR   AlphaFoldDB; G3F5K2; -.
DR   GO; GO:0016705; F:oxidoreductase activity, acting on paired donors, with incorporation or reduction of molecular oxygen; IDA:UniProtKB.
DR   GO; GO:0016117; P:carotenoid biosynthetic process; IDA:UniProtKB.
DR   InterPro; IPR005804; FA_desaturase_dom.
DR   InterPro; IPR012171; Fatty_acid_desaturase.
DR   PANTHER; PTHR19353; PTHR19353; 2.
DR   Pfam; PF00487; FA_desaturase; 2.
PE   1: Evidence at protein level;
KW   Carotenoid biosynthesis; Oxidoreductase.
FT   CHAIN           1..387
FT                   /note="Beta-carotene 4-ketolase"
FT                   /id="PRO_0000452213"
FT   REGION          1..78
FT                   /note="Disordered"
FT                   /evidence="ECO:0000256|SAM:MobiDB-lite"
FT   COMPBIAS        1..15
FT                   /note="Basic and acidic residues"
FT                   /evidence="ECO:0000256|SAM:MobiDB-lite"
FT   COMPBIAS        36..78
FT                   /note="Polar residues"
FT                   /evidence="ECO:0000256|SAM:MobiDB-lite"
SQ   SEQUENCE   387 AA;  44107 MW;  316696A64525217D CRC64;
     MPHSIDMEDS SAIAERSKHA GLALEPEACF NLPQPTAEDR QDNWQTQYHS SEGAQGGSRK
     AQAADATTGN PTVDDASQQN GLLQQWVKQG YFMPAEHGSK AGNDVKHKYS PPKSDVWGVL
     VACTVITTWA ALFYHSIFQI KLPSIEQLRS GNYNPSDFTS WPHVLLAFFS LEFLYTGLFI
     TTHDAMHGTI AMRHRKLNDF LGSFAISLYA WFDYKMLHKK HWEHHNHTGK VGADPDFHRG
     NPSILPWFAR FMMEYSSLWQ FAKIAWWATG MQLLGAPFQN ILMFMTAAPI LSAFRLFYYG
     TYIPHHPEPG PASDKVEMDW TMSRTSTAPS LLSFLTCYHF DLHWEHHRWP YAPWWQLPVC
     RKLAGRTNPL HTEALQTAEP SRLEHGG