ICS1_CAMIR
ID ICS1_CAMIR Reviewed; 365 AA.
AC Q2HXL9;
DT 10-FEB-2021, integrated into UniProtKB/Swiss-Prot.
DT 21-MAR-2006, sequence version 1.
DT 03-AUG-2022, entry version 38.
DE RecName: Full=7-methylxanthine methyltransferase ICS1 {ECO:0000303|PubMed:16333668};
DE Short=TCS1b {ECO:0000303|PubMed:26773541};
DE EC=2.1.1.159 {ECO:0000269|PubMed:16333668};
DE AltName: Full=Theobromine synthase ICS1 {ECO:0000303|PubMed:16333668};
GN Name=ICS1 {ECO:0000303|PubMed:16333668};
GN Synonyms=TCS1B {ECO:0000303|PubMed:26773541};
OS Camellia irrawadiensis (Burmese tea).
OC Eukaryota; Viridiplantae; Streptophyta; Embryophyta; Tracheophyta;
OC Spermatophyta; Magnoliopsida; eudicotyledons; Gunneridae; Pentapetalae;
OC asterids; Ericales; Theaceae; Camellia.
OX NCBI_TaxID=153142;
RN [1]
RP NUCLEOTIDE SEQUENCE [MRNA], FUNCTION, CATALYTIC ACTIVITY, PATHWAY, AND
RP BIOPHYSICOCHEMICAL PROPERTIES.
RX PubMed=16333668; DOI=10.1007/s00438-005-0070-z;
RA Yoneyama N., Morimoto H., Ye C.-X., Ashihara H., Mizuno K., Kato M.;
RT "Substrate specificity of N-methyltransferase involved in purine alkaloids
RT synthesis is dependent upon one amino acid residue of the enzyme.";
RL Mol. Genet. Genomics 275:125-135(2006).
RN [2]
RP GENE FAMILY, AND NOMENCLATURE.
RX PubMed=26773541; DOI=10.1016/j.plaphy.2015.12.020;
RA Jin J.-Q., Yao M.-Z., Ma C.-L., Ma J.-Q., Chen L.;
RT "Natural allelic variations of TCS1 play a crucial role in caffeine
RT biosynthesis of tea plant and its related species.";
RL Plant Physiol. Biochem. 100:18-26(2016).
CC -!- FUNCTION: Involved in the biosynthesis of caffeine (PubMed:16333668).
CC Catalyzes the conversion of 7-methylxanthine (7mX) to theobromine, to
CC some extent, able to convert paraxanthine to caffeine and, slightly,
CC mediates the conversion of theobromine to caffeine (PubMed:16333668).
CC {ECO:0000269|PubMed:16333668}.
CC -!- CATALYTIC ACTIVITY:
CC Reaction=1,7-dimethylxanthine + S-adenosyl-L-methionine = caffeine +
CC H(+) + S-adenosyl-L-homocysteine; Xref=Rhea:RHEA:10280,
CC ChEBI:CHEBI:15378, ChEBI:CHEBI:25858, ChEBI:CHEBI:27732,
CC ChEBI:CHEBI:57856, ChEBI:CHEBI:59789;
CC Evidence={ECO:0000269|PubMed:16333668};
CC PhysiologicalDirection=left-to-right; Xref=Rhea:RHEA:10281;
CC Evidence={ECO:0000269|PubMed:16333668};
CC -!- CATALYTIC ACTIVITY:
CC Reaction=S-adenosyl-L-methionine + theobromine = caffeine + H(+) + S-
CC adenosyl-L-homocysteine; Xref=Rhea:RHEA:20944, ChEBI:CHEBI:15378,
CC ChEBI:CHEBI:27732, ChEBI:CHEBI:28946, ChEBI:CHEBI:57856,
CC ChEBI:CHEBI:59789; Evidence={ECO:0000269|PubMed:16333668};
CC PhysiologicalDirection=left-to-right; Xref=Rhea:RHEA:20945;
CC Evidence={ECO:0000269|PubMed:16333668};
CC -!- CATALYTIC ACTIVITY:
CC Reaction=7-methylxanthine + S-adenosyl-L-methionine = H(+) + S-
CC adenosyl-L-homocysteine + theobromine; Xref=Rhea:RHEA:24604,
CC ChEBI:CHEBI:15378, ChEBI:CHEBI:28946, ChEBI:CHEBI:48991,
CC ChEBI:CHEBI:57856, ChEBI:CHEBI:59789; EC=2.1.1.159;
CC Evidence={ECO:0000269|PubMed:16333668};
CC PhysiologicalDirection=left-to-right; Xref=Rhea:RHEA:24605;
CC Evidence={ECO:0000269|PubMed:16333668};
CC -!- COFACTOR:
CC Name=Mg(2+); Xref=ChEBI:CHEBI:18420;
CC Evidence={ECO:0000250|UniProtKB:Q9FLN8};
CC Note=Binds 1 Mg(2+) ion per subunit. {ECO:0000250|UniProtKB:Q9FLN8};
CC -!- BIOPHYSICOCHEMICAL PROPERTIES:
CC Kinetic parameters:
CC KM=51 uM for 7-methylxanthine (in the presence of 50 uM S-adenosyl-L-
CC methionine) {ECO:0000269|PubMed:16333668};
CC pH dependence:
CC Optimum pH is 8.0-8.5. {ECO:0000269|PubMed:16333668};
CC -!- PATHWAY: Alkaloid biosynthesis. {ECO:0000269|PubMed:16333668}.
CC -!- SIMILARITY: Belongs to the methyltransferase superfamily. Type-7
CC methyltransferase family. {ECO:0000305}.
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DR EMBL; AB056108; BAE79729.1; -; mRNA.
DR AlphaFoldDB; Q2HXL9; -.
DR SMR; Q2HXL9; -.
DR BRENDA; 2.1.1.160; 8604.
DR GO; GO:0046872; F:metal ion binding; IEA:UniProtKB-KW.
DR GO; GO:0008168; F:methyltransferase activity; IEA:UniProtKB-KW.
DR GO; GO:0032259; P:methylation; IEA:UniProtKB-KW.
DR Gene3D; 1.10.1200.270; -; 1.
DR Gene3D; 3.40.50.150; -; 1.
DR InterPro; IPR005299; MeTrfase_7.
DR InterPro; IPR042086; MeTrfase_capping.
DR InterPro; IPR029063; SAM-dependent_MTases_sf.
DR PANTHER; PTHR31009; PTHR31009; 1.
DR Pfam; PF03492; Methyltransf_7; 1.
DR SUPFAM; SSF53335; SSF53335; 1.
PE 1: Evidence at protein level;
KW Magnesium; Metal-binding; Methyltransferase; Transferase.
FT CHAIN 1..365
FT /note="7-methylxanthine methyltransferase ICS1"
FT /id="PRO_0000451788"
FT BINDING 19
FT /ligand="S-adenosyl-L-methionine"
FT /ligand_id="ChEBI:CHEBI:59789"
FT /evidence="ECO:0000250|UniProtKB:A4GE70"
FT BINDING 19
FT /ligand="substrate"
FT /evidence="ECO:0000250|UniProtKB:A4GE70"
FT BINDING 22..26
FT /ligand="substrate"
FT /evidence="ECO:0000250|UniProtKB:A4GE69"
FT BINDING 61..62
FT /ligand="S-adenosyl-L-methionine"
FT /ligand_id="ChEBI:CHEBI:59789"
FT /evidence="ECO:0000250|UniProtKB:Q9FLN8"
FT BINDING 61
FT /ligand="S-adenosyl-L-methionine"
FT /ligand_id="ChEBI:CHEBI:59789"
FT /evidence="ECO:0000250|UniProtKB:A4GE69"
FT BINDING 62
FT /ligand="S-adenosyl-L-methionine"
FT /ligand_id="ChEBI:CHEBI:59789"
FT /evidence="ECO:0000250|UniProtKB:A0A6C0WW36"
FT BINDING 67
FT /ligand="S-adenosyl-L-methionine"
FT /ligand_id="ChEBI:CHEBI:59789"
FT /evidence="ECO:0000250|UniProtKB:A4GE70"
FT BINDING 97..100
FT /ligand="S-adenosyl-L-methionine"
FT /ligand_id="ChEBI:CHEBI:59789"
FT /evidence="ECO:0000250|UniProtKB:A4GE69"
FT BINDING 134..136
FT /ligand="S-adenosyl-L-methionine"
FT /ligand_id="ChEBI:CHEBI:59789"
FT /evidence="ECO:0000250|UniProtKB:A4GE69"
FT BINDING 151..153
FT /ligand="S-adenosyl-L-methionine"
FT /ligand_id="ChEBI:CHEBI:59789"
FT /evidence="ECO:0000250|UniProtKB:A4GE69"
FT BINDING 152..156
FT /ligand="substrate"
FT /evidence="ECO:0000250|UniProtKB:A4GE69"
FT BINDING 173
FT /ligand="Mg(2+)"
FT /ligand_id="ChEBI:CHEBI:18420"
FT /evidence="ECO:0000250|UniProtKB:Q9FLN8"
FT BINDING 259
FT /ligand="Mg(2+)"
FT /ligand_id="ChEBI:CHEBI:18420"
FT /evidence="ECO:0000250|UniProtKB:Q9FLN8"
FT BINDING 261
FT /ligand="Mg(2+)"
FT /ligand_id="ChEBI:CHEBI:18420"
FT /evidence="ECO:0000250|UniProtKB:Q9FLN8"
FT BINDING 262
FT /ligand="Mg(2+)"
FT /ligand_id="ChEBI:CHEBI:18420"
FT /evidence="ECO:0000250|UniProtKB:Q9FLN8"
FT SITE 149
FT /note="Involved in substrate discrimination"
FT /evidence="ECO:0000250|UniProtKB:Q9FZN8"
FT SITE 221
FT /note="Involved in substrate discrimination"
FT /evidence="ECO:0000250|UniProtKB:Q2HXI6"
FT SITE 265
FT /note="Involved in substrate discrimination"
FT /evidence="ECO:0000250|UniProtKB:Q9FZN8"
FT SITE 313
FT /note="Involved in substrate discrimination"
FT /evidence="ECO:0000250|UniProtKB:Q9FZN8"
FT SITE 328
FT /note="Involved in substrate discrimination"
FT /evidence="ECO:0000250|UniProtKB:Q9FZN8"
SQ SEQUENCE 365 AA; 40937 MW; 98434FFC08889215 CRC64;
MGKVNEVLFM NRGEGEISYA QNSAFTQKVA SMAMPALENA VETLFSKDFH LLQALTAADL
GCAAGPNTFA VISTIKRMME KKCRELYCQT LELQVYLNDL FGNDFNTLFK GLSSEVVGNK
CEEVSCYVMG VPGSFHGRLF PRNSLHLVHS SYSVHWLTQA PKGLTSREGL ALNKGKIYIS
KTSPPVVKEA YLSQFHEDFT MFLNARSQEV VPNGCMVLIL HGRQSSDPSE MESCFTWELL
AIAIAELVSQ GLIDEDKLDT FNVPSYWPSL EEVKDIVERD GSFTIDHLEG FELDSLEMQE
NDKWVRGDKF AKMVRAFTEP IISNQFGHEI MDKLYDKFTH ILVSDLEAEL PKTTSIILVL
SKIVG
