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Information on EC 1.14.18.10 - plant 4,4-dimethylsterol C-4alpha-methyl-monooxygenase and Organism(s) Arabidopsis thaliana and UniProt Accession Q8L7W5
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1.14.18.10 plant 4,4-dimethylsterol C-4alpha-methyl-monooxygenaseIUBMB Comments
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.
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Word Map
- 1.14.18.10
- ergosterol
-
demethylation
-
c4-methyl
- squalene
-
glabra2
-
acyl-coa-binding
-
histidine-rich
- cycloartenol
The taxonomic range for the selected organisms is: Arabidopsis thaliana
The enzyme appears in selected viruses and cellular organisms
The enzyme appears in selected viruses and cellular organisms
Reaction Schemes
hide(Overall reactions are displayed. Show all >>)
Synonyms
smo1-2, smo1-1, erg25a, 4alpha-methyl oxidase, sterol methyl oxidase, smo1-3, erg25b, 4,4-dimethylsterol-4alpha-methyl oxidase, sterol-4alpha-methyl oxidase, sterol-4alpha-methyl oxidase 1, 
more
topSYNONYM 
ORGANISM
UNIPROT
COMMENTARY 
LITERATURE
SMO1
SMO1
-
-
-
-
REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
PATHWAY SOURCE
PATHWAYS
-
-, -, -, -
SYSTEMATIC NAME
IUBMB Comments
24-methylidenecycloartanol,ferrocytochrome-b5:oxygen oxidoreductase (C-4alpha-methyl-hydroxylating)
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.
SUBSTRATE
PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
3beta-hydroxy-4beta-methyl-5alpha-cholest-7-ene-4alpha-carbaldehyde + a ferrocytochrome + O2
3beta-hydroxy-4beta-methyl-5alpha-cholest-7-ene-4alpha-carboxylate + a ferricytochrome + H2O
step 3 of 3 of the overall reaction
-
-
?
4,4-dimethyl-5alpha-cholest-7-en-3beta-ol + a ferrocytochrome + O2
4beta-hydroxymethyl-4alpha-methyl-5alpha-cholest-7-en-3beta-ol + a ferricytochrome + H2O
step 1 of 3 of the overall reaction
-
-
?
4beta-hydroxymethyl-4alpha-methyl-5alpha-cholest-7-en-3beta-ol + a ferrocytochrome + O2
3beta-hydroxy-4beta-methyl-5alpha-cholest-7-ene-4alpha-carbaldehyde + a ferricytochrome + H2O
step 2 of 3 of the overall reaction
-
-
?
24-methylidenecycloartanol + 6 ferrocytochrome b5 + 3 O2 + 6 H+
3beta-hydroxy-4beta,14alpha-dimethyl-9beta,19-cyclo-5alpha-ergost-24(241)-ene-4alpha-carboxylate + 6 ferricytochrome b5 + 4 H2O
overall reaction
-
-
ir
3beta-hydroxy-4beta-methyl-5alpha-cholest-7-ene-4alpha-carbaldehyde + a ferricytochrome + H+ + O2
3beta-hydroxy-4beta-methyl-5alpha-cholest-7-ene-4alpha-carboxylate + a ferrocytochrome + H2O
1c
-
-
?
3beta-hydroxy-4beta-methyl-5alpha-cholest-7-ene-4alpha-carbaldehyde + a ferrocytochrome + O2
3beta-hydroxy-4beta-methyl-5alpha-cholest-7-ene-4alpha-carboxylate + a ferricytochrome + H2O
step 3 of 3 of the overall reaction
-
-
?
4,4-dimethyl-5alpha-cholest-7-en-3beta-ol + a ferrocytochrome + 3 H+ + 3 O2
3beta-hydroxy-4beta-methyl-5alpha-cholest-7-ene-4alpha-carboxylate + a ferricytochrome + 4 H2O
overall reaction
-
-
?
4,4-dimethyl-5alpha-cholest-7-en-3beta-ol + a ferrocytochrome + H+ + O2
4alpha-hydroxymethyl-4beta-methyl-5alpha-cholest-7-en-3beta-ol + a ferricytochrome + H2O
1a
-
-
?
4,4-dimethyl-5alpha-cholest-7-en-3beta-ol + a ferrocytochrome + O2
4beta-hydroxymethyl-4alpha-methyl-5alpha-cholest-7-en-3beta-ol + a ferricytochrome + H2O
step 1 of 3 of the overall reaction
-
-
?
4alpha-hydroxymethyl-4beta-methyl-5alpha-cholest-7-en-3beta-ol + reduced acceptor + H+ + O2
3beta-hydroxy-4beta-methyl-5alpha-cholest-7-ene-4alpha-carbaldehyde + acceptor + 2 H2O
1b
-
-
?
4beta-hydroxymethyl-4alpha-methyl-5alpha-cholest-7-en-3beta-ol + a ferrocytochrome + O2
3beta-hydroxy-4beta-methyl-5alpha-cholest-7-ene-4alpha-carbaldehyde + a ferricytochrome + H2O
step 2 of 3 of the overall reaction
-
-
?
additional information
?
-
-
conversion of cycloartenol into functional phytosterol requires the removal of 2 methyl groups at C4 by the enzymic complex including the sterol 4alpha-methyl oxidase SMO
-
-
?
additional information
?
-
conversion of cycloartenol into functional phytosterol requires the removal of 2 methyl groups at C4 by the enzymic complex including the sterol 4alpha-methyl oxidase SMO
-
-
?
additional information
?
-
conversion of cycloartenol into functional phytosterol requires the removal of 2 methyl groups at C4 by the enzymic complex including the sterol 4alpha-methyl oxidase SMO
-
-
?
additional information
?
-
conversion of cycloartenol into functional phytosterol requires the removal of 2 methyl groups at C4 by the enzymic complex including the sterol 4alpha-methyl oxidase SMO
-
-
?
additional information
?
-
-
conversion of cycloartenol into functional phytosterol requires the removal of 2 methyl groups at C4 by the enzymic complex including the sterol 4alpha-methyl oxidase SMO
-
-
?
additional information
?
-
conversion of cycloartenol into functional phytosterol requires the removal of 2 methyl groups at C4 by the enzymic complex including the sterol 4alpha-methyl oxidase SMO
-
-
?
additional information
?
-
conversion of cycloartenol into functional phytosterol requires the removal of 2 methyl groups at C4 by the enzymic complex including the sterol 4alpha-methyl oxidase SMO
-
-
?
additional information
?
-
conversion of cycloartenol into functional phytosterol requires the removal of 2 methyl groups at C4 by the enzymic complex including the sterol 4alpha-methyl oxidase SMO
-
-
?
additional information
?
-
-
the enzyme is unable to oxidize 4,4-dimethylzymosterol
-
-
?
NATURAL SUBSTRATE
NATURAL PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
24-methylidenecycloartanol + 6 ferrocytochrome b5 + 3 O2 + 6 H+
3beta-hydroxy-4beta,14alpha-dimethyl-9beta,19-cyclo-5alpha-ergost-24(241)-ene-4alpha-carboxylate + 6 ferricytochrome b5 + 4 H2O
overall reaction
-
-
ir
additional information
?
-
-
conversion of cycloartenol into functional phytosterol requires the removal of 2 methyl groups at C4 by the enzymic complex including the sterol 4alpha-methyl oxidase SMO
-
-
?
additional information
?
-
conversion of cycloartenol into functional phytosterol requires the removal of 2 methyl groups at C4 by the enzymic complex including the sterol 4alpha-methyl oxidase SMO
-
-
?
additional information
?
-
conversion of cycloartenol into functional phytosterol requires the removal of 2 methyl groups at C4 by the enzymic complex including the sterol 4alpha-methyl oxidase SMO
-
-
?
additional information
?
-
conversion of cycloartenol into functional phytosterol requires the removal of 2 methyl groups at C4 by the enzymic complex including the sterol 4alpha-methyl oxidase SMO
-
-
?
additional information
?
-
-
conversion of cycloartenol into functional phytosterol requires the removal of 2 methyl groups at C4 by the enzymic complex including the sterol 4alpha-methyl oxidase SMO
-
-
?
additional information
?
-
conversion of cycloartenol into functional phytosterol requires the removal of 2 methyl groups at C4 by the enzymic complex including the sterol 4alpha-methyl oxidase SMO
-
-
?
additional information
?
-
conversion of cycloartenol into functional phytosterol requires the removal of 2 methyl groups at C4 by the enzymic complex including the sterol 4alpha-methyl oxidase SMO
-
-
?
additional information
?
-
conversion of cycloartenol into functional phytosterol requires the removal of 2 methyl groups at C4 by the enzymic complex including the sterol 4alpha-methyl oxidase SMO
-
-
?
COFACTOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
METALS and IONS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
INHIBITOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
additional information
-
not inhibited by stigmastan-3beta,5alpha,6alpha-triol
-
ORGANISM
COMMENTARY
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
isozyme SMO1-1; 2 distinct enzyme families exist with 3 and 2 isozymes belonging to them, respectively
SwissProt
LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY
GeneOntology No.
LITERATURE
SOURCE
UNIPROT
ENTRY NAME
ORGANISM
NO. OF AA
NO. OF TRANSM. HELICES
MOLECULAR WEIGHT[Da]
SOURCE
SEQUENCE
LOCALIZATION PREDICTION
The reliability class of the localization prediction ranges from 1 (very reliable) to 5 (not reliable).
The reliability class of the localization prediction ranges from 1 (very reliable) to 5 (not reliable). SMO11_ARATH
298
4
34647
Swiss-Prot
other Location (Reliability: 2)
SUBUNIT
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
additional information
additional information
-
enzyme possesses 3 His-rich motifs common for membrane-bound non-heme iron oxygenases
additional information
enzyme possesses 3 His-rich motifs common for membrane-bound non-heme iron oxygenases
additional information
enzyme possesses 3 His-rich motifs common for membrane-bound non-heme iron oxygenases
additional information
enzyme possesses 3 His-rich motifs common for membrane-bound non-heme iron oxygenases
additional information
-
enzyme possesses 3 His-rich motifs common for membrane-bound non-heme iron oxygenases
additional information
enzyme possesses 3 His-rich motifs common for membrane-bound non-heme iron oxygenases
additional information
enzyme possesses 3 His-rich motifs common for membrane-bound non-heme iron oxygenases
additional information
enzyme possesses 3 His-rich motifs common for membrane-bound non-heme iron oxygenases
CLONED (Commentary)
ORGANISM
UNIPROT
LITERATURE
DNA and amino acid sequence determination and analysis, expression in enzyme-lacking Saccharomyces cerevisiae strain erg25
DNA and amino acid sequence determination and analysis, expression in enzyme-lacking Saccharomyces cerevisiae strain erg25
REF.
AUTHORS
TITLE
JOURNAL
VOL.
PAGES
YEAR
ORGANISM (UNIPROT)
PUBMED ID
SOURCE
Darnet, S.; Rahier, A.
Plant sterol biosynthesis: identification of two distinct families of sterol 4alpha-methyl oxidases
Biochem. J.
378
889-898
2004
Arabidopsis thaliana, Arabidopsis thaliana (F4JLZ6), Arabidopsis thaliana (Q1EC69), Arabidopsis thaliana (Q8L7W5), Nicotiana benthamiana (Q5J955), Nicotiana benthamiana, Nicotiana tabacum (Q6YAU5), Zea mays, Zea mays SMO1
Rahier, A.
Dissecting the sterol C-4 demethylation process in higher plants. from structures and genes to catalytic mechanism
Steroids
76
340-352
2011
Arabidopsis thaliana
Darnet, S.; Bard, M.; Rahier, A.
Functional identification of sterol-4alpha-methyl oxidase cDNAs from Arabidopsis thaliana by complementation of a yeast erg25 mutant lacking sterol-4alpha-methyl oxidation
FEBS Lett.
508
39-43
2001
Arabidopsis thaliana (Q8VWZ8), Arabidopsis thaliana (Q9ZW22), Arabidopsis thaliana
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