KEGG   ORTHOLOGY: K14423
Entry
K14423                      KO                                     

Name
SMO1
Definition
plant 4,4-dimethylsterol C-4alpha-methyl-monooxygenase [EC:1.14.18.10]
Pathway
ko00100  Steroid biosynthesis
ko01100  Metabolic pathways
ko01110  Biosynthesis of secondary metabolites
Module
M00917  Phytosterol biosynthesis, squalene 2,3-epoxide => campesterol/sitosterol
Brite
KEGG Orthology (KO) [BR:ko00001]
 09100 Metabolism
  09103 Lipid metabolism
   00100 Steroid biosynthesis
    K14423  SMO1; plant 4,4-dimethylsterol C-4alpha-methyl-monooxygenase
Enzymes [BR:ko01000]
 1. Oxidoreductases
  1.14  Acting on paired donors, with incorporation or reduction of molecular oxygen
   1.14.18  With another compound as one donor, and incorporation of one atom of oxygen into the other donor
    1.14.18.10  plant 4,4-dimethylsterol C-4alpha-methyl-monooxygenase
     K14423  SMO1; plant 4,4-dimethylsterol C-4alpha-methyl-monooxygenase
Other DBs
RN: R12377
Genes
ATH: AT4G12110(SMO1-1) AT4G22755 AT4G22756(SMO1-2)
ALY: 110226378 110226382 9310821
CRB: 111829641 111829642 17878277 17884650
CSAT: 104707512 104717801 104718035 104718036 104720179 104722765 104722766 104722767 104731224 104731225 104733374 104737226
EUS: EUTSA_v10024722mg EUTSA_v10025849mg EUTSA_v10028846mg
BRP: 103853483 103860261 103860313
BNA: 106375731 106375734 106376549 106376550 106395025 106440893 106440900
BOE: 106323132 106323529 106326927
RSZ: 108819044 108822182 108826950
THJ: 104813000 104813925
LJA: Lj4g3v1302690.1(Lj4g3v1302690.1)
CSV: 101211692
CMO: 103490939
MCHA: 111020420
QSU: 111999469
VVI: 100255536
LSV: 111918756
DOSA: Os03t0108500-01(Os03g0108500) Os10t0545200-01(Os10g0545200)
OBR: 102723086
ATS: 109735447(LOC109735447) 109742913(LOC109742913) 109743100(LOC109743100) 109752552(LOC109752552) 109759404(LOC109759404)
DCT: 110101909
PEQ: 110036326
ATR: 18441549
 » show all
Reference
  Authors
Darnet S, Rahier A
  Title
Plant sterol biosynthesis: identification of two distinct families of sterol 4alpha-methyl oxidases.
  Journal
Biochem J 378:889-98 (2004)
DOI:10.1042/BJ20031572
  Sequence
Reference
  Authors
Rahier A
  Title
Dissecting the sterol C-4 demethylation process in higher plants. From structures and genes to catalytic mechanism.
  Journal
Steroids 76:340-52 (2011)
DOI:10.1016/j.steroids.2010.11.011

KEGG   ENZYME: 1.14.18.10
Entry
EC 1.14.18.10               Enzyme                                 

Name
plant 4,4-dimethylsterol C-4alpha-methyl-monooxygenase;
SMO1 (gene name)
Class
Oxidoreductases;
Acting on paired donors, with incorporation or reduction of molecular oxygen;
With another compound as one donor, and incorporation of one atom of oxygen into the other donor
Sysname
24-methylidenecycloartanol,ferrocytochrome-b5:oxygen oxidoreductase (C-4alpha-methyl-hydroxylating)
Reaction(IUBMB)
24-methylidenecycloartanol + 6 ferrocytochrome b5 + 3 O2 + 6 H+ = 3beta-hydroxy-4beta,14alpha-dimethyl-9beta,19-cyclo-5alpha-ergost-24(241)-en-4alpha-carboxylate + 6 ferricytochrome b5 + 4 H2O (overall reaction) [RN:R12377];
(1a) 24-methylidenecycloartanol + 2 ferrocytochrome b5 + O2 + 2 H+ = 4alpha-(hydroxymethyl)-4beta,14alpha-dimethyl-9beta,19-cyclo-5alpha-ergost-24(241)-en-3beta-ol + 2 ferricytochrome b5 + H2O [RN:R12368];
(1b) 4alpha-(hydroxymethyl)-4beta,14alpha-dimethyl-9beta,19-cyclo-5alpha-ergost-24(241)-en-3beta-ol + 2 ferrocytochrome b5 + O2 + 2 H+ = 4alpha-formyl-4beta,14alpha-dimethyl-9beta,19-cyclo-5alpha-ergost-24(241)-en-3beta-ol + 2 ferricytochrome b5 + 2 H2O [RN:R12369];
(1c) 4alpha-formyl-4beta,14alpha-dimethyl-9beta,19-cyclo-5alpha-ergost-24(241)-en-3beta-ol + 2 ferrocytochrome b5 + O2 + 2 H+ = 3beta-hydroxy-4beta,14alpha-dimethyl-9beta,19-cyclo-5alpha-ergost-24(241)-en-4alpha-carboxylate + 2 ferricytochrome b5 + H2O [RN:R12370]
Reaction(KEGG)
Substrate
24-methylidenecycloartanol [CPD:C08830];
ferrocytochrome b5 [CPD:C00999];
O2 [CPD:C00007];
H+ [CPD:C00080];
4alpha-(hydroxymethyl)-4beta,14alpha-dimethyl-9beta,19-cyclo-5alpha-ergost-24(241)-en-3beta-ol;
4alpha-formyl-4beta,14alpha-dimethyl-9beta,19-cyclo-5alpha-ergost-24(241)-en-3beta-ol
Product
3beta-hydroxy-4beta,14alpha-dimethyl-9beta,19-cyclo-5alpha-ergost-24(241)-en-4alpha-carboxylate;
ferricytochrome b5 [CPD:C00996];
H2O [CPD:C00001];
4alpha-(hydroxymethyl)-4beta,14alpha-dimethyl-9beta,19-cyclo-5alpha-ergost-24(241)-en-3beta-ol;
4alpha-formyl-4beta,14alpha-dimethyl-9beta,19-cyclo-5alpha-ergost-24(241)-en-3beta-ol
Comment
This plant enzyme catalyses a step in the biosynthesis of sterols. It acts on the 4alpha-methyl group of the 4,4-dimethylated intermediate 24-methylidenecycloartanol and catalyses three successive oxidations, turning it into a carboxyl group. The carboxylate is subsequently removed by EC 1.1.1.418, plant 3beta-hydroxysteroid-4alpha-carboxylate 3-dehydrogenase (decarboxylating), which also catalyses the epimerization of the remaining 4beta-methyl into the 4alpha position. Unlike the fungal/animal enzyme EC 1.14.18.9, 4alpha-methylsterol monooxygenase, this enzyme is not able to remove the methyl group from C-4-monomethylated substrates. That activity is performed in plants by a second enzyme, EC 1.14.18.11, plant 4alpha-monomethylsterol monooxygenase.
History
EC 1.14.18.10 created 2019
Pathway
ec00100  Steroid biosynthesis
ec01100  Metabolic pathways
ec01110  Biosynthesis of secondary metabolites
Orthology
K14423  plant 4,4-dimethylsterol C-4alpha-methyl-monooxygenase
Genes
ATH: AT4G12110(SMO1-1) AT4G22755 AT4G22756(SMO1-2)
ALY: 110226378 110226382 9310821
CRB: 111829641 111829642 17878277 17884650
CSAT: 104707512 104717801 104718035 104718036 104720179 104722765 104722766 104722767 104731224 104731225 104733374 104737226
EUS: EUTSA_v10024722mg EUTSA_v10025849mg EUTSA_v10028846mg
BRP: 103853483 103860261 103860313
BNA: 106375731 106375734 106376549 106376550 106395025 106440893 106440900
BOE: 106323132 106323529 106326927
RSZ: 108819044 108822182 108826950
THJ: 104813000 104813925
LJA: Lj4g3v1302690.1(Lj4g3v1302690.1)
CSV: 101211692
CMO: 103490939
MCHA: 111020420
QSU: 111999469
VVI: 100255536
LSV: 111918756
DOSA: Os03t0108500-01(Os03g0108500) Os10t0545200-01(Os10g0545200)
OBR: 102723086
ATS: 109735447(LOC109735447) 109742913(LOC109742913) 109743100(LOC109743100) 109752552(LOC109752552) 109759404(LOC109759404)
DCT: 110101909
PEQ: 110036326
ATR: 18441549
 » show all
Reference
1  [PMID:8505296]
  Authors
Pascal S, Taton M, Rahier A.
  Title
Plant sterol biosynthesis. Identification and characterization of two distinct microsomal oxidative enzymatic systems involved in sterol C4-demethylation.
  Journal
J Biol Chem 268:11639-54 (1993)
Reference
2  [PMID:9240456]
  Authors
Rahier A, Smith M, Taton M.
  Title
The role of cytochrome b5 in 4alpha-methyl-oxidation and C5(6) desaturation of plant sterol precursors.
  Journal
Biochem Biophys Res Commun 236:434-7 (1997)
DOI:10.1006/bbrc.1997.6974
Reference
3  [PMID:11707264]
  Authors
Darnet S, Bard M, Rahier A
  Title
Functional identification of sterol-4alpha-methyl oxidase cDNAs from Arabidopsis  thaliana by complementation of a yeast erg25 mutant lacking sterol-4alpha-methyl  oxidation.
  Journal
FEBS Lett 508:39-43 (2001)
DOI:10.1016/S0014-5793(01)03002-2
Reference
4  [PMID:14653780]
  Authors
Darnet S, Rahier A
  Title
Plant sterol biosynthesis: identification of two distinct families of sterol 4alpha-methyl oxidases.
  Journal
Biochem J 378:889-98 (2004)
DOI:10.1042/BJ20031572
  Sequence
Other DBs
ExplorEnz - The Enzyme Database: 1.14.18.10
IUBMB Enzyme Nomenclature: 1.14.18.10
ExPASy - ENZYME nomenclature database: 1.14.18.10
BRENDA, the Enzyme Database: 1.14.18.10

KEGG   REACTION: R12377
Entry
R12377                      Reaction                               

Name
24-methylidenecycloartanol,ferrocytochrome-b5:oxygen oxidoreductase (C-4alpha-methyl-hydroxylating)
Definition
24-Methylidenecycloartanol + 6 Ferrocytochrome b5 + 3 Oxygen + 6 H+ <=> 3beta-Hydroxy-4beta,14alpha-dimethyl-9beta,19-cyclo-5alpha-ergost-24(24(1))-en-4alpha-carboxylate + 6 Ferricytochrome b5 + 4 H2O
Equation
C08830 + 6 C00999 + 3 C00007 + 6 C00080 <=> C22116 + 6 C00996 + 4 C00001
Comment
three-step reaction (see R12368+R12369+R12370)
Reaction class
RC01952  C08830_C22116
Enzyme
Pathway
rn00100  Steroid biosynthesis
rn01100  Metabolic pathways
rn01110  Biosynthesis of secondary metabolites
Module
M00917  Phytosterol biosynthesis, squalene 2,3-epoxide => campesterol/sitosterol
Orthology
K14423  plant 4,4-dimethylsterol C-4alpha-methyl-monooxygenase [EC:1.14.18.10]

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