AC MF_01032; DC Protein; auto TR HAMAP; MF_01032; -; 1; level=0 XX Names: LeuD_type2 XX case ID HACB DE RecName: Full=Methanogen homoaconitase small subunit; DE Short=HACN; DE EC=4.2.1.114; DE AltName: Full=Homoaconitate hydratase; GN Name=hacB; else ID LEUD DE RecName: Full=3-isopropylmalate dehydratase small subunit; DE EC=4.2.1.33; DE AltName: Full=Alpha-IPM isomerase; DE Short=IPMI; DE AltName: Full=Isopropylmalate isomerase; GN Name=leuD; end case XX case CC -!- FUNCTION: Hydro-lyase with broad substrate specificity for cis- CC unsaturated tricarboxylic acids. Catalyzes both the reversible CC dehydration of (R)-homocitrate ((R)-2-hydroxybutane-1,2,4- CC tricarboxylate) to produce cis-homoaconitate ((Z)-but-1-ene-1,2,4- CC tricarboxylate), and its hydration to homoisocitrate ((1R,2S)-1- CC hydroxybutane-1,2,4-tricarboxylate). Is also able to hydrate the CC analogous longer chain substrates cis-homo(2)-aconitate, cis-homo(3)- CC aconitate. All these reactions are part of the biosynthesis pathway of CC coenzyme B. CC -!- CATALYTIC ACTIVITY: CC Reaction=(2R)-homocitrate = (2R,3S)-homoisocitrate; CC Xref=Rhea:RHEA:32303, ChEBI:CHEBI:15404, ChEBI:CHEBI:58884; CC EC=4.2.1.114; CC -!- PATHWAY: Organic acid metabolism; 2-oxosuberate biosynthesis. CC -!- SUBUNIT: Heterotetramer of 2 HacA and 2 HacB proteins. else CC -!- FUNCTION: Catalyzes the isomerization between 2-isopropylmalate and 3- CC isopropylmalate, via the formation of 2-isopropylmaleate. CC -!- CATALYTIC ACTIVITY: CC Reaction=(2R,3S)-3-isopropylmalate = (2S)-2-isopropylmalate; CC Xref=Rhea:RHEA:32287, ChEBI:CHEBI:1178, ChEBI:CHEBI:35121; CC EC=4.2.1.33; CC -!- PATHWAY: Amino-acid biosynthesis; L-leucine biosynthesis; L-leucine CC from 3-methyl-2-oxobutanoate: step 2/4. CC -!- SUBUNIT: Heterodimer of LeuC and LeuD. end case CC -!- SIMILARITY: Belongs to the LeuD family. LeuD type 2 subfamily. XX DR Pfam; PF00694; Aconitase_C; 1; trigger=no DR NCBIfam; TIGR02084; leud; 1; trigger=no DR NCBIfam; TIGR02087; LEUD_arch; 1; trigger=no XX case not KW Amino-acid biosynthesis KW Branched-chain amino acid biosynthesis KW Leucine biosynthesis end case KW Lyase XX case GO GO:0004409; F:homoaconitate hydratase activity GO GO:0019298; P:coenzyme B biosynthetic process else GO GO:0003861; F:3-isopropylmalate dehydratase activity GO GO:0009098; P:leucine biosynthetic process end case XX FT From: HACB_METJA (Q58667) case or or or FT MOTIF 24..27 FT /note="YLRT" FT Tag: HACNmotif; Optional; Condition: Y-L-R-T FT SITE 26 FT /note="Critical for substrate specificity" FT Optional; Condition: R end case XX Size: 161-208; Related: MF_01031; Template: P04787; Q58667; Scope: Bacteria Archaea Fusion: Nter: None Cter: None Duplicate: in ARCFU, DEIRA, METAC, METJA, METKA, METMA, METTH, PYRAB, PYRFU, THEMA Plasmid: None Comments: The family member in THET2 is shown to function as a homoaconitase (for lysine biosynthesis), as well as one of the 2 copies found in METJA that catalyzes both the dehydration of (R)-homocitrate and the hydration of cis-homoaconitate for coenzyme B biosynthesis. The other copy in METJA functions both in leucine and isoleucine biosynthesis, since it catalyzes the isomerization between 2-isopropylmalate and 3-isopropylmalate and between 2-methylmalate and 3-methylmalate. In Archaea, a motif that indicates the protein specificity has been determined (see PubMed=20170198): the presence of the YLRT motif likely indicates HACN activity, while proteins with the YLV(Y/I/M) sequence are IPMIs enzymes. XX # Revision 1.32 2023/06/01 //