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EC 1.1.1.170 Details
EC number
1.1.1.170
Accepted name
3β-hydroxysteroid-4α-carboxylate 3-dehydrogenase (decarboxylating)
Reaction
a 3β-hydroxysteroid-4α-carboxylate + NAD(P)+ = a 3-oxosteroid + CO2 + NAD(P)H
Other name(s)
3β-hydroxy-4β-methylcholestenecarboxylate 3-dehydrogenase (decarboxylating), 3β-hydroxy-4β-methylcholestenoate dehydrogenase, sterol 4α-carboxylic decarboxylase, sterol-4α-carboxylate 3-dehydrogenase (decarboxylating) (ambiguous), ERG26 (gene name), NSDHL (gene name)
Systematic name
3β-hydroxysteroid-4α-carboxylate:NAD(P)+ 3-oxidoreductase (decarboxylating)
CAS registry number
71822-23-6
Comment
The enzyme participates in the biosynthesis of several important sterols such as ergosterol and cholesterol. It is part of a three enzyme system that removes methyl groups from the C-4 position of steroid molecules. The first enzyme, EC 1.14.18.9, 4α-methylsterol monooxygenase, catalyses three successive oxidations of the methyl group, resulting in a carboxyl group; the second enzyme, EC 1.1.1.170, catalyses an oxidative decarboxylation that results in a reduction of the 3β-hydroxy group at the C-3 carbon to an oxo group; and the last enzyme, EC 1.1.1.270, 3β-hydroxysteroid 3-dehydrogenase, reduces the 3-oxo group back to a 3β-hydroxyl. If a second methyl group remains at the C-4 position, this enzyme also catalyses its epimerization from 4β to 4α orientation, so it could serve as a substrate for a second round of demethylation. cf. EC 1.1.1.418, plant 3β-hydroxysteroid-4α-carboxylate 3-dehydrogenase (decarboxylating).
History
created 1978, modified 2002, modified 2012, modified 2019
EC Tree
1.1.1.68 created 1965, deleted 1978 [transferred to EC 1.1.99.15, deleted 1980]
1.1.1.70 created 1965, deleted 1978
1.1.1.74 created 1972, deleted 1976
1.1.1.89 created 1972, deleted 1976
1.1.1.109 created 1972, deleted 1976
1.1.1.139 created 1972, deleted 1978
1.1.1.155 created 1976, deleted 2004
1.1.1.171 created 1978, deleted 1984
1.1.1.180 created 1983, deleted 1984
1.1.1.182 created 1983, deleted 1990
1.1.1.204 created 1972 as EC 1.2.1.37, transferred 1984 to EC 1.1.1.204, modified 1989, deleted 2004
1.1.1.242 created 1992, deleted 2001
1.1.1.249 provisional version created 1999, deleted 1999 (reinstated 2001 as EC 2.5.1.46)
1.1.1.253 created 1999, deleted 2003