Enzymes
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- Name help_outline cycloartenol Identifier CHEBI:17030 (CAS: 469-38-5) help_outline Charge 0 Formula C30H50O InChIKeyhelp_outline ONQRKEUAIJMULO-YBXTVTTCSA-N SMILEShelp_outline [C@]123[C@@]4([C@](C([C@@H](O)CC4)(C)C)(CC[C@]1([C@]5([C@@]([C@@]([C@@H](CCC=C(C)C)C)(CC5)[H])(CC2)C)C)[H])[H])C3 2D coordinates Mol file for the small molecule Search links Involved in 3 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline S-adenosyl-L-methionine Identifier CHEBI:59789 Charge 1 Formula C15H23N6O5S InChIKeyhelp_outline MEFKEPWMEQBLKI-AIRLBKTGSA-O SMILEShelp_outline C[S+](CC[C@H]([NH3+])C([O-])=O)C[C@H]1O[C@H]([C@H](O)[C@@H]1O)n1cnc2c(N)ncnc12 2D coordinates Mol file for the small molecule Search links Involved in 842 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline cyclolaudenol Identifier CHEBI:142990 (CAS: 511-61-5) help_outline Charge 0 Formula C31H52O InChIKeyhelp_outline IXHACUTUTOCSJE-HWTFXIFRSA-N SMILEShelp_outline C1[C@]23[C@@]4(CC[C@]5([C@]([C@@]4(CC[C@]2(C([C@H](C1)O)(C)C)[H])[H])(CC[C@@]5([C@@H](CC[C@@H](C(=C)C)C)C)[H])C)C)C3 2D coordinates Mol file for the small molecule Search links Involved in 1 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 9,176 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline S-adenosyl-L-homocysteine Identifier CHEBI:57856 Charge 0 Formula C14H20N6O5S InChIKeyhelp_outline ZJUKTBDSGOFHSH-WFMPWKQPSA-N SMILEShelp_outline Nc1ncnc2n(cnc12)[C@@H]1O[C@H](CSCC[C@H]([NH3+])C([O-])=O)[C@@H](O)[C@H]1O 2D coordinates Mol file for the small molecule Search links Involved in 768 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
Cross-references
| RHEA:13137 | RHEA:13138 | RHEA:13139 | RHEA:13140 | |
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| Reaction direction help_outline | undefined | left-to-right | right-to-left | bidirectional |
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Publications
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Sterol C-methyl transferase from Prototheca wickerhamii mechanism, sterol specificity and inhibition.
Mangla A.T., Nes W.D.
The membrane-bound sterol methyl transferase (SMT) enzyme from Prototheca wickerhamii, a non-photosynthetic, yeast-like alga, was found to C-methylate appropriate delta24(25)-sterol acceptor molecules to delta25(27)-24beta-methyl products stereoselectively. Incubation with pairs of substrates--[2H ... >> More
The membrane-bound sterol methyl transferase (SMT) enzyme from Prototheca wickerhamii, a non-photosynthetic, yeast-like alga, was found to C-methylate appropriate delta24(25)-sterol acceptor molecules to delta25(27)-24beta-methyl products stereoselectively. Incubation with pairs of substrates--[2H3-methyl]AdoMet and cycloartenol, and AdoMet and [27-(13)C]lanosterol--followed by 1H and 13C NMR analysis of the isotopically labeled products demonstrated the si-face (beta-face attack) mechanism of C-methylation and the regiospecificity of delta25(27)-double bond formation from the pro-Z methyl group (C27) on lanosterol. The enzyme has a substrate preference for a sterol with a 3beta-hydroxyl group, a planar nucleus and a side chain oriented into a 'right-handed' structure (20R-chirality) characteristic of the native substrate, cycloartenol. The apparent native molecular weight of the SMT was determined to be approximately 154,000, as measured by Superose 6 FPLC. A series of sterol analogues which contain heteroatoms substituted for C24 and C25 or related structural modifications, including steroidal alkaloids, havs been used to probe further the active site and mechanism of action of the SMT enzyme. Sterol side chains containing isoelectronic modifications of a positively charged moiety in the form of an ammonium group substituted for carbon at C25, C24, C23 or C22 are particularly potent non-competitive inhibitors (Ki for the most potent inhibitor tested, 25-azacycloartanol, was ca. 2 nM, four orders of magnitude less than the Km for cycloartenol of 28 microM), supporting the intermediacy of the 24-methyl C24(25)-carbenium ion intermediate. Ergosterol, but neither cholesterol nor sitosterol, was found to inhibit SMT activity (Ki = 80 microM). The combination of results suggests that the interrelationships of substrate functional groups within the active center of a delta24(25) to delta25(27) 24beta-methyl-SMT could be approximated thereby allowing the rational design of C-methylation inhibitors to be formulated and tested. << Less
Bioorg Med Chem 8:925-936(2000) [PubMed] [EuropePMC]
This publication is cited by 1 other entry.