Lanosterol 14-a-demethylase

Lanosterol 14-a demethylase MCSS/Ludi Probe mapping + fragment linking [106]... 

Burton PM, Swinney DC, Heller R, Dunlap B, Chiou M, et al. 1995. Azalanstat (RS-21607), a lanosterol 14 alpha-demethylase inhibitor with cholesterol-lowering activity. Biochem Pharmacol 50 529-544. 

Rozman D, Stromstedt M, Waterman MR. 1996. The three human cytochrome P450 lanosterol 14 alpha-demethylase (CYP51) genes reside on chromosomes 3, 7, and 13 structure of the two retrotransposed pseudogenes, association with a line-1 element, and evolution of the human CYP51 family. Arch Biochem Biophys 333 466-474. 

Stromstedt M, Rozman D, Waterman MR. 1996. The ubiquitously expressed human CYP51 encodes lanosterol 14 alpha-demethylase, a cytochrome P450 whose expression is regulated by oxysterols. Arch Biochem Biophys 329 73-81. 

Lewis, D. F. V., Wiseman, A., and Tarbit, M. H. (1999) Molecular modeling of lanosterol 14-alpha-demethylase (CYP51) from Saccharomyces cerevisiae via homology with CYP102, a unique bacterial cytochrome P450 isoform quantitative structure-activity relationships (QSARs) within two related series of antifungal azole derivatives../. Enz. Inhib. 14, 175-192. 

Trosken, E.R., Adamska, M., Arand, M., Zarn, J.A., Patten, G., Volkel, W. and Lutz, W.K. (2006) Comparison of lanosterol-14 alpha-demethylase (CYP51) of human and Candida albicans for inhibition by different antifungal azoles. Toxicology, 228, 24-32. 

Holtje HD, Fattorusso C. Construction of a model of the Candida albicans lanosterol 14-alpha-demethylase active site using the homology modelling technique. Pharm Acta Helv 1998 72 271-277. 

Mode of action Ketoconazole interacts with C-14 a-demethylase (a cytochrome P-450 enzyme) to block demethylation of lanosterol to ergosterol, the principal sterol of fungal membranes Figure 34.4). This inhibition disrupts membrane function and increases permeability. Ketoconazole acts in an additive manner with flucytosine against Candida, but antagonizes amphotericin B s antifungal activity. 

Shyadehi, A.Z., D.C. Lamb, S.L. Kelly, D.E. Kelly, W.H. Schunck, and J.N. Wright et al. (1996). The mechanism of the acyl-carbon bond cleavage reaction catalyzed by recombinant sterol 14a-demethylase of Candida albicans (other names are Lanosterol 14 alpha-demethylase, P-45014DM, and CYP51). J. Biol. Chem. 271, 12445-12450. 

Azoles are fungicidal and interfere with the synthesis of ergosterol by inhibiting 14-a-demethylase, a fungal P450 enzyme, which converts lanosterol to ergosterol... 

Walker KA, Kertesz DJ, Rotstein DM et al. Selective inhibition of mammalian lanosterol 14 alpha-demethylase A possible strategy for cholesterol lowering. J Med Chem 1993 36 2235-37. 

A less common reactive species is the Fe peroxo anion expected from two-electron reduction of O2 at a hemoprotein iron atom (Fig. 14, structure A). Protonation of this intermediate would yield the Fe —OOH precursor (Fig. 14, structure B) of the ferryl species. However, it is now clear that the Fe peroxo anion can directly react as a nucleophile with highly electrophilic substrates such as aldehydes. Addition of the peroxo anion to the aldehyde, followed by homolytic scission of the dioxygen bond, is now accepted as the mechanism for the carbon-carbon bond cleavage reactions catalyzed by several cytochrome P450 enzymes, including aromatase, lanosterol 14-demethylase, and sterol 17-lyase (133). A similar nucleophilic addition of the Fe peroxo anion to a carbon-nitrogen double bond has been invoked in the mechanism of the nitric oxide synthases (133). 

Aoyama, Y., Funae, Y, Noshiro, M., Horiuchi, T. and Yoshida, Y. (1994) Occurrence of a P450 showing high homology to yeast lanosterol 14-demethylase (P450(14DM)) in the rat liver. Biochem. Biophys. Res. Commun., 201, 1320-6. 

Figure 7.34. Competitive inhibitors of lanosterol 14-demethylase. The group R on the sterols is either C(CH3)CH2CH2CH2C(CHj)2 or a close variant. Fluconazole and miconazole are clinically employed as antifungal agents.

Fischer RT, Stam SH, Johnson PR et al. Mechanistic studies of lanosterol 14 alpha-methyl demethylase Substrate requirements for the component reactions catalyzed by a single cytochrome... 

Another example for the cleavage of C-C bonds via multiple substrate oxidations is the demethylation of lanosterol to a precursor of cholesterol, 4,4-dimethyl-5a-cholesta-8,14,24-diene-3p-ol, catalyzed by a lanosterol 14a-demethylase (CYP51) [39]. The mechanism includes three steps and proceeds via initial hydroxylation of the C14 methyl group (corresponds to C32 hydroxylation), followed by further oxidation of the alcohol to the aldehyde. Finally, acyl cleavage occurs, leading to the formation of a double bond in the steroid (Scheme 5.8). 

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