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MetaCyc Enzyme: 4-α-methyl-Δ7-sterol-4α-methyl oxidase

Gene: SMO2-1 Accession Number: AT1G07420 (MetaCyc)

Synonyms: sterol 4α-methyl oxidase

Species: Arabidopsis thaliana col

Summary:
Several lines of evidence suggest that this enzyme is involved in the second of two demethylation steps that occur during plant sterol biosynthesis [Darnet04]. It should be capable of performing the reaction: 4α-methyl-δ7-sterol + 3 NADPH + 3H+ + 3 O2 -> a 4α-carboxy, δ-7-sterol + 3 NADP+ + 3 H2O.

Enzymes of this class carry out three successive monooxygenation steps on the methyl group causing it to undergo the following series of changes: CH3->CH2OH->CHO->COOH. The final product of these reactions can then be acted on by a 3β-hydroxysteroid-dehydrogenase/C4-decarboxylase and a 3-keto-reductase to produce the final demethylated product [Darnet04].

To date, no direct assays of this enzyme's activities have been performed. However, it can complement an erg25 yeast mutant by promoting the biosynthesis of ergosterol [Darnet01]. This is not a typical plant sterol, but it does have structural similarity to several plant sterols such as sitosterol and stigmasterol.

Unification Links: PhylomeDB:Q8VWZ8 , Phytozome Plant Orthologs:AT1G07420.1 , Pride:Q8VWZ8 , String:3702.AT1G07420.1-P , TAIR:AT1G07420 , UniProt:Q8VWZ8

Relationship Links: InterPro:IN-FAMILY:IPR006694 , Pfam:IN-FAMILY:PF04116

Gene-Reaction Schematic: ?

Gene-Reaction Schematic

Credits:
Created 07-Jan-2011 by Dreher KA , TAIR


Enzymatic reaction of: 4α-formyl-5α-cholesta-7,24-dien-3β-ol-4α-methyl oxidase (4-α-methyl-Δ7-sterol-4α-methyl oxidase)

EC Number: 1.14.13.-

4α-formyl-5α-cholesta-7,24-dien-3β-ol + NADH + oxygen <=> 4α-carboxy-5α-cholesta-7,24-dien-3β-ol + NAD+ + H2O

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is physiologically favored in the direction shown.


Enzymatic reaction of: 4α-hydroxymethyl-5α-cholesta-7,24-dien-3β-ol-4α-methyl oxidase (4-α-methyl-Δ7-sterol-4α-methyl oxidase)

EC Number: 1.14.13.-

4α-hydroxymethyl-5α-cholesta-7,24-dien-3β-ol + NADH + oxygen + H+ <=> 4α-formyl-5α-cholesta-7,24-dien-3β-ol + NAD+ + 2 H2O

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is physiologically favored in the direction shown.


Enzymatic reaction of: 4α-methyl-5α-cholesta-7,24-dien-3β-ol-4α-methyl oxidase (4-α-methyl-Δ7-sterol-4α-methyl oxidase)

EC Number: 1.14.13.-

4α-methyl-5α-cholesta-7,24-dien-3β-ol + NADH + oxygen + H+ <=> 4α-hydroxymethyl-5α-cholesta-7,24-dien-3β-ol + NAD+ + H2O

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is physiologically favored in the direction shown.


Enzymatic reaction of: 4α-formyl-stigmasta-7,24(241)-dien-3β-ol-methyl oxidase (4-α-methyl-Δ7-sterol-4α-methyl oxidase)

EC Number: 1.14.13.-

4α-formyl-stigmasta-7,24(241)-dien-3β-ol + NADH + oxygen <=> 4α-carboxy-stigmasta-7,24(241)-dien-3β-ol + NAD+ + H2O

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is physiologically favored in the direction shown.

In Pathways: plant sterol biosynthesis


Enzymatic reaction of: 4α-hydroxymethyl-stigmasta-7,24(241)-dien-3β-ol-methyl oxidase (4-α-methyl-Δ7-sterol-4α-methyl oxidase)

EC Number: 1.14.13.-

4α-hydroxymethyl-stigmasta-7,24(241)-dien-3β-ol + NADH + oxygen + H+ <=> 4α-formyl-stigmasta-7,24(241)-dien-3β-ol + NAD+ + 2 H2O

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is physiologically favored in the direction shown.

In Pathways: plant sterol biosynthesis

Citations: [Darnet04]


Enzymatic reaction of: 24-ethylidenelophenol 4α-methyl oxidase (4-α-methyl-Δ7-sterol-4α-methyl oxidase)

EC Number: 1.14.13.-

24-ethylidenelophenol + NADH + oxygen + H+ <=> 4α-hydroxymethyl-stigmasta-7,24(241)-dien-3β-ol + NAD+ + H2O

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is physiologically favored in the direction shown.

In Pathways: plant sterol biosynthesis


Enzymatic reaction of: 4α-formyl-ergosta-7,24(241)-dien-3β-ol-methyl oxidase (4-α-methyl-Δ7-sterol-4α-methyl oxidase)

EC Number: 1.14.13.-

4α-formyl-ergosta-7,24(241)-dien-3β-ol + NADH + oxygen <=> 4α-carboxy-ergosta-7,24(241)-dien-3β-ol + NAD+ + H2O

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is physiologically favored in the direction shown.

In Pathways: plant sterol biosynthesis


Enzymatic reaction of: 4α-hydroxymethyl-ergosta-7,24(241)-dien-3β-ol-methyl oxidase (4-α-methyl-Δ7-sterol-4α-methyl oxidase)

EC Number: 1.14.13.-

4α-hydroxymethyl-ergosta-7,24(241)-dien-3β-ol + NADH + oxygen + H+ <=> 4α-formyl-ergosta-7,24(241)-dien-3β-ol + NAD+ + 2 H2O

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is physiologically favored in the direction shown.

In Pathways: plant sterol biosynthesis

Citations: [Darnet04]


Enzymatic reaction of: 24-methylenelophenol methyl oxidase (4-α-methyl-Δ7-sterol-4α-methyl oxidase)

EC Number: 1.14.13.-

24-methylenelophenol + NADH + oxygen + H+ <=> 4α-hydroxymethyl-ergosta-7,24(241)-dien-3β-ol + NAD+ + H2O

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is physiologically favored in the direction shown.

In Pathways: plant sterol biosynthesis


References

Darnet01: Darnet S, Bard M, Rahier A (2001). "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(1);39-43. PMID: 11707264

Darnet04: Darnet S, Rahier A (2004). "Plant sterol biosynthesis: identification of two distinct families of sterol 4alpha-methyl oxidases." Biochem J 378(Pt 3);889-98. PMID: 14653780


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Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by SRI International Pathway Tools version 19.0 on Tue Jun 30, 2015, BIOCYC13B.