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EC 1.14.13.246 Details
show Brenda entryEC number
1.14.13.246
Accepted name
4β-methylsterol monooxygenase
Reaction
a 3β-hydroxy-4,4-dimethylsteroid + 3 NADH + 3 H+ + 3 O2 = a 3β-hydroxy-4α-methylsteroid-4β-carboxylate + 3 NAD+ + 4 H2O (overall reaction);;(1a) a 3β-hydroxy-4,4-dimethylsteroid + NADH + H+ + O2 = a 3β-hydroxy-4β-hydroxymethyl-4α-methylsteroid + NAD+ + H2O;;(1b) a 3β-hydroxy-4β-hydroxymethyl-4α-methylsteroid + NADH + H+ + O2 = a 3β-hydroxy-4β-formyl-4α-methylsteroid + NAD+ + 2 H2O;;(1c) a 3β-hydroxy-4β-formyl-4α-methylsteroid + NADH + H+ + O2 = a 3β-hydroxy-4α-methylsteroid-4β-carboxylate + NAD+ + H2O
Other name(s)
sdmA (gene name)
Systematic name
3β-hydroxy-4,4-dimethylsteroid,NADH:oxygen oxidoreductase (C-4mβ-hydroxylating)
Comment
Contains a Rieske [2Fe-2S] iron-sulfur cluster. This bacterial enzyme (SdmA) participates in the biosynthesis of bacterial sterols. Together with SdmB it forms an enzyme system that removes one methyl group from the C-4 position of 4,4-dimethylated steroid molecules. SdmA catalyses three successive oxidations of the C-4β methyl group, turning it into a carboxylate group; the second enzyme, SdmB, is a bifunctional enzyme that catalyses two different activities. As EC 1.1.1.417, 3β-hydroxysteroid-4β-carboxylate 3-dehydrogenase (decarboxylating), it catalyses an oxidative decarboxylation that results in reduction of the 3β-hydroxy group at the C-3 carbon to an oxo group. As EC 1.1.1.270, 3β-hydroxysteroid 3-dehydrogenase, it reduces the 3-oxo group back to a 3β-hydroxyl. Unlike the animal/fungal enzyme EC 1.14.18.9, 4α-methylsterol monooxygenase, and the plant enzymes EC 1.14.18.10, plant 4,4-dimethylsterol C-4α-methyl-monooxygenase, and EC 1.14.18.11, plant 4α-monomethylsterol monooxygenase, this enzyme acts preferentially on the 4β-methyl group. Since no epimerization of the remaining C-4α methyl group occurs, the enzyme can only remove one methyl group, leaving a 4α-monomethylated product. Known substrates include 4,4-dimethyl-5α-cholest-8-en-3β-ol and 14-demethyllanosterol.
History
created 2019
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1 Oxidoreductases
1.1 Acting on the CH-OH group of donors
1.6.4.1 created 1961, deleted 2002 1.6.4.2 created 1961, modified 1989, deleted 2002 1.6.4.3 created 1961, modified 1976, deleted 1983 1.6.4.4 created 1965, deleted 2002 1.6.4.5 created 1972, deleted 2002 1.6.4.6 created 1972, deleted 2002 1.6.4.7 created 1978, deleted 2002 1.6.4.8 created 1989, deleted 2002 1.6.4.9 created 1992, deleted 2002 1.6.4.10 created 1992, deleted 2002 1.14.13.45 created 1992, deleted 2003
