ID   LACB_LACLL              Reviewed;         171 AA.
AC   P23495;
DT   01-NOV-1991, integrated into UniProtKB/Swiss-Prot.
DT   01-NOV-1991, sequence version 1.
DT   25-MAY-2022, entry version 84.
DE   RecName: Full=Galactose-6-phosphate isomerase subunit LacB {ECO:0000255|HAMAP-Rule:MF_01556};
DE            EC=5.3.1.26 {ECO:0000255|HAMAP-Rule:MF_01556};
GN   Name=lacB {ECO:0000255|HAMAP-Rule:MF_01556};
OS   Lactococcus lactis subsp. lactis (Streptococcus lactis).
OG   Plasmid pLP712.
OC   Bacteria; Firmicutes; Bacilli; Lactobacillales; Streptococcaceae;
OC   Lactococcus.
OX   NCBI_TaxID=1360;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA], FUNCTION, SUBUNIT, OPERON STRUCTURE, AND
RP   INDUCTION.
RC   STRAIN=MG1820;
RX   PubMed=1901863; DOI=10.1016/s0021-9258(20)89626-4;
RA   van Rooijen R.J., van Schalkwijk S., de Vos W.M.;
RT   "Molecular cloning, characterization, and nucleotide sequence of the
RT   tagatose 6-phosphate pathway gene cluster of the lactose operon of
RT   Lactococcus lactis.";
RL   J. Biol. Chem. 266:7176-7181(1991).
CC   -!- CATALYTIC ACTIVITY:
CC       Reaction=aldehydo-D-galactose 6-phosphate = keto-D-tagatose 6-
CC         phosphate; Xref=Rhea:RHEA:13033, ChEBI:CHEBI:58255,
CC         ChEBI:CHEBI:134283; EC=5.3.1.26; Evidence={ECO:0000255|HAMAP-
CC         Rule:MF_01556};
CC   -!- PATHWAY: Carbohydrate metabolism; D-galactose 6-phosphate degradation;
CC       D-tagatose 6-phosphate from D-galactose 6-phosphate: step 1/1.
CC       {ECO:0000255|HAMAP-Rule:MF_01556}.
CC   -!- SUBUNIT: Heteromultimeric protein consisting of LacA and LacB.
CC       {ECO:0000255|HAMAP-Rule:MF_01556, ECO:0000269|PubMed:1901863}.
CC   -!- INDUCTION: By lactose. The operon consists of lacABCDFEGX.
CC       {ECO:0000269|PubMed:1901863}.
CC   -!- MISCELLANEOUS: This gene was sequenced from pMG820, a laboratory-
CC       derived deletion of the naturally occurring plasmid pLP712.
CC   -!- SIMILARITY: Belongs to the LacAB/RpiB family. {ECO:0000255|HAMAP-
CC       Rule:MF_01556}.
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DR   EMBL; M60447; AAA25178.1; -; Genomic_DNA.
DR   EMBL; M65190; AAA25169.1; -; Genomic_DNA.
DR   PIR; B39778; B39778.
DR   RefSeq; YP_005863085.1; NC_017478.1.
DR   AlphaFoldDB; P23495; -.
DR   SMR; P23495; -.
DR   KEGG; ag:AAA25178; -.
DR   BRENDA; 5.3.1.26; 2903.
DR   UniPathway; UPA00702; UER00714.
DR   GO; GO:0050044; F:galactose-6-phosphate isomerase activity; IEA:UniProtKB-UniRule.
DR   GO; GO:0019388; P:galactose catabolic process; IEA:UniProtKB-UniPathway.
DR   GO; GO:0019512; P:lactose catabolic process via tagatose-6-phosphate; IEA:UniProtKB-UniRule.
DR   Gene3D; 3.40.1400.10; -; 1.
DR   HAMAP; MF_01556; LacB; 1.
DR   InterPro; IPR004784; LacB.
DR   InterPro; IPR003500; RpiB_LacA_LacB.
DR   InterPro; IPR036569; RpiB_LacA_LacB_sf.
DR   PANTHER; PTHR30345; PTHR30345; 1.
DR   Pfam; PF02502; LacAB_rpiB; 1.
DR   PIRSF; PIRSF005384; RpiB_LacA_B; 1.
DR   SUPFAM; SSF89623; SSF89623; 1.
DR   TIGRFAMs; TIGR01119; lacB; 1.
DR   TIGRFAMs; TIGR00689; rpiB_lacA_lacB; 1.
PE   1: Evidence at protein level;
KW   Isomerase; Lactose metabolism; Plasmid.
FT   CHAIN           1..171
FT                   /note="Galactose-6-phosphate isomerase subunit LacB"
FT                   /id="PRO_0000208135"
SQ   SEQUENCE   171 AA;  18926 MW;  BE323E0690CEAE13 CRC64;
     MRIAIGCDHI VTDVKMAVSE FLKSKGYEVL DFGTYDHVRT HYPIYGKKVG EAVVSGQADL
     GVCICGTGVG INNAVNKVPG VRSALVRDMT SALYAKEELN ANVIGFGGMI TGGLLMNDII
     EAFIEAEYKP TEENKKLIAK IEHVETHNAH QADEEFFTEF LEKWDRGEYH D