KEGG   ENZYME: 1.14.18.11Help
Entry
EC 1.14.18.11               Enzyme                                 

Name
plant 4alpha-monomethylsterol monooxygenase;
SMO2 (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
BRITE hierarchy
Sysname
24-ethylidenelophenol,ferrocytochrome-b5:oxygen oxidoreductase (C-4alpha-methyl-hydroxylating)
Reaction(IUBMB)
24-methylidenelophenol + 6 ferrocytochrome b5 + 3 O2 + 6 H+ = 3beta-hydroxyergosta-7,24(241)-dien-4alpha-carboxylate + 6 ferricytochrome b5 + 4 H2O (overall reaction) [RN:R12378];
(1a) 24-methylidenelophenol + 2 ferrocytochrome b5 + O2 + 2 H+ = 4alpha-(hydroxymethyl)ergosta-7,24(241)-dien-3beta-ol + 2 ferricytochrome b5 + H2O [RN:R12372];
(1b) 4alpha-(hydroxymethyl)ergosta-7,24(241)-dien-3beta-ol + 2 ferrocytochrome b5 + O2 + 2 H+ = 4alpha-formylergosta-7,24(241)-dien-3beta-ol + 2 ferricytochrome b5 + 2 H2O [RN:R12373];
(1c) 4alpha-formylergosta-7,24(241)-dien-3beta-ol + 2 ferrocytochrome b5 + O2 + 2 H+ = 3beta-hydroxyergosta-7,24(241)-dien-4alpha-carboxylate + 2 ferricytochrome b5 + H2O [RN:R12374]
Reaction(KEGG)
Substrate
24-methylidenelophenol [CPD:C11522];
ferrocytochrome b5 [CPD:C00999];
O2 [CPD:C00007];
H+ [CPD:C00080];
4alpha-(hydroxymethyl)ergosta-7,24(241)-dien-3beta-ol;
4alpha-formylergosta-7,24(241)-dien-3beta-ol
Product
3beta-hydroxyergosta-7,24(241)-dien-4alpha-carboxylate;
ferricytochrome b5 [CPD:C00996];
H2O [CPD:C00001];
4alpha-(hydroxymethyl)ergosta-7,24(241)-dien-3beta-ol;
4alpha-formylergosta-7,24(241)-dien-3beta-ol
Comment
This plant enzyme catalyses a step in the biosynthesis of sterols. It acts on the methyl group of the 4alpha-methylated intermediates 24-ethylidenelophenol and 24-methylidenelophenol 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). Unlike the fungal/animal enzyme EC 1.14.18.9, 4alpha-methylsterol monooxygenase, this enzyme is not able to act on 4,4-dimethylated substrates. That activity, which occurs earlier in the pathway, is performed in plants by a second enzyme, EC 1.14.18.10, plant 4,4-dimethylsterol C-4alpha-methyl-monooxygenase.
History
EC 1.14.18.11 created 2019
Pathway
ec00100  Steroid biosynthesis
ec01100  Metabolic pathways
ec01110  Biosynthesis of secondary metabolites
Orthology
K14424  plant 4alpha-monomethylsterol monooxygenase
Genes
ATH: AT1G07420(SMO2-1) AT2G29390(SMO2-2)
ALY: ARALYDRAFT_481856 ARALYDRAFT_887953(SMO2-2)
CRB: 17887780 17900058
CSAT: 104700565 104739310 104739311 104749943 104754908 104778598 104786746
EUS: EUTSA_v10008485mg EUTSA_v10017113mg
BRP: 103836444 103843947 103864965
BNA: 106362242 106362243 106391117 106402219 106420038 106450049 106450054 106453376 111208485
BOE: 106307917 106310476 106336604 106344016
RSZ: 108813689 108819536 108848436 108851590 108859993
THJ: 104815774 104826306
CPAP: 110812189
CIT: 102611328
TCC: 18590619
EGR: 104422462
LJA: Lj2g3v1375520.1(Lj2g3v1375520.1) Lj2g3v1375540.1(Lj2g3v1375540.1)
FVE: 101303960
RCN: 112201412
PPER: 18773152
PMUM: 103321848
PAVI: 110773473
ZJU: 107410870
CSV: 101220009
CMO: 103497129
MCHA: 111024686
RCU: 8284099
JCU: 105629916
SIND: 105170642
BVG: 104900049
SOE: 110787672
DOSA: Os07t0101500-01(Os07g0101500) Os11t0707600-01(Os11g0707600)
BDI: 100835573
ATS: 109757775(LOC109757775)
SBI: 8061435
ZMA: 100281761 542766(gpm633)
DCT: 110099264
PEQ: 110021891
ATR: 18436262
DFA: DFA_11723
 » show all
Taxonomy
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
  Sequence
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: 1.14.18.11
IUBMB Enzyme Nomenclature: 1.14.18.11
ExPASy - ENZYME nomenclature database: 1.14.18.11
BRENDA, the Enzyme Database: 1.14.18.11
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