Enzymes
| UniProtKB help_outline | 405 proteins |
Reaction participants Show >> << Hide
- Name help_outline O2 Identifier CHEBI:15379 (CAS: 7782-44-7) help_outline Charge 0 Formula O2 InChIKeyhelp_outline MYMOFIZGZYHOMD-UHFFFAOYSA-N SMILEShelp_outline O=O 2D coordinates Mol file for the small molecule Search links Involved in 2,709 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline pregnenolone Identifier CHEBI:16581 (Beilstein: 2059026; CAS: 145-13-1) help_outline Charge 0 Formula C21H32O2 InChIKeyhelp_outline ORNBQBCIOKFOEO-QGVNFLHTSA-N SMILEShelp_outline [H][C@@]12CC=C3C[C@@H](O)CC[C@]3(C)[C@@]1([H])CC[C@]1(C)[C@H](CC[C@@]21[H])C(C)=O 2D coordinates Mol file for the small molecule Search links Involved in 7 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
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Namehelp_outline
reduced [NADPH—hemoprotein reductase]
Identifier
RHEA-COMP:11964
Reactive part
help_outline
- Name help_outline FMNH2 Identifier CHEBI:57618 (Beilstein: 6258176) help_outline Charge -2 Formula C17H21N4O9P InChIKeyhelp_outline YTNIXZGTHTVJBW-SCRDCRAPSA-L SMILEShelp_outline Cc1cc2Nc3c([nH]c(=O)[nH]c3=O)N(C[C@H](O)[C@H](O)[C@H](O)COP([O-])([O-])=O)c2cc1C 2D coordinates Mol file for the small molecule Search links Involved in 794 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline 17α-hydroxypregnenolone Identifier CHEBI:28750 (Beilstein: 2337329; CAS: 387-79-1) help_outline Charge 0 Formula C21H32O3 InChIKeyhelp_outline JERGUCIJOXJXHF-TVWVXWENSA-N SMILEShelp_outline CC(=O)[C@@]1(O)CC[C@H]2[C@@H]3CC=C4C[C@@H](O)CC[C@]4(C)[C@H]3CC[C@]12C 2D coordinates Mol file for the small molecule Search links Involved in 2 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline H+ Identifier CHEBI:15378 Charge 1 Formula H InChIKeyhelp_outline GPRLSGONYQIRFK-UHFFFAOYSA-N SMILEShelp_outline [H+] 2D coordinates Mol file for the small molecule Search links Involved in 9,431 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline H2O Identifier CHEBI:15377 (Beilstein: 3587155; CAS: 7732-18-5) help_outline Charge 0 Formula H2O InChIKeyhelp_outline XLYOFNOQVPJJNP-UHFFFAOYSA-N SMILEShelp_outline [H]O[H] 2D coordinates Mol file for the small molecule Search links Involved in 6,204 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
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Namehelp_outline
oxidized [NADPH—hemoprotein reductase]
Identifier
RHEA-COMP:11965
Reactive part
help_outline
- Name help_outline FMN Identifier CHEBI:58210 Charge -3 Formula C17H18N4O9P InChIKeyhelp_outline ANKZYBDXHMZBDK-SCRDCRAPSA-K SMILEShelp_outline C12=NC([N-]C(C1=NC=3C(N2C[C@@H]([C@@H]([C@@H](COP(=O)([O-])[O-])O)O)O)=CC(=C(C3)C)C)=O)=O 2D coordinates Mol file for the small molecule Search links Involved in 804 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
Cross-references
| RHEA:50236 | RHEA:50237 | RHEA:50238 | RHEA:50239 | |
|---|---|---|---|---|
| Reaction direction help_outline | undefined | left-to-right | right-to-left | bidirectional |
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| MetaCyc help_outline |
Related reactions help_outline
More general form(s) of this reaction
Publications
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Cytochrome b5 augments the 17,20-lyase activity of human P450c17 without direct electron transfer.
Auchus R.J., Lee T.C., Miller W.L.
In the biosynthesis of steroid hormones, P450c17 is the single enzyme that catalyzes both the 17alpha-hydroxylation of 21-carbon steroids and the 17,20-lyase activity that cleaves the C17-C20 bond to produce C19 sex steroids. Cytochrome b5 augments the 17,20-lyase activity of cytochrome P450c17 in ... >> More
In the biosynthesis of steroid hormones, P450c17 is the single enzyme that catalyzes both the 17alpha-hydroxylation of 21-carbon steroids and the 17,20-lyase activity that cleaves the C17-C20 bond to produce C19 sex steroids. Cytochrome b5 augments the 17,20-lyase activity of cytochrome P450c17 in vitro, but this has not been demonstrated in membranes, and the mechanism of this action is unknown. We expressed human P450c17, human P450-oxidoreductase (OR), and/or human cytochrome b5 in Saccharomyces cerevisiae and analyzed the 17alpha-hydroxylase and 17,20-lyase activities of the resulting yeast microsomes. Yeast expressing only P450c17 have 17alpha-hydroxylase and trace 17,20-lyase activities toward both Delta4 and Delta5 steroids. Coexpression of human OR with P450c17 increases the Vmax of both the 17alpha-hydroxylase and 17,20-lyase reactions 5-fold; coexpression of human b5 with P450c17 also increases the Vmax of the 17,20-lyase reactions but not of the 17alpha-hydroxylase reactions. Simultaneous expression of human b5 with P450c17 and OR, or addition of purified human b5 to microsomes from yeast coexpressing human P450c17 and OR, further increases the Vmax of the 17,20-lyase reaction without altering 17alpha-hydroxylase activity. Genetically engineered yeast and mixing experiments demonstrate that OR is both necessary and sufficient for microsomal 17,20-lyase activity. Addition of purified human holo-b5, apo-b5, or cytochrome c to microsomes containing both human P450c17 and OR demonstrate that the stimulatory action of b5 does not require electron transfer from b5 to P450c17. These data suggest that human b5 acts principally as an allosteric effector that interacts primarily with the P450c17.OR complex to stimulate 17, 20-lyase activity. << Less
J. Biol. Chem. 273:3158-3165(1998) [PubMed] [EuropePMC]
This publication is cited by 3 other entries.