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. 1979 Nov 1;183(2):309–315. doi: 10.1042/bj1830309

Studies on the mechanism of lanosterol 14 alpha-demethylation. A requirement for two distinct types of mixed-function-oxidase systems.

F G Gibbons, C R Pullinger, K A Mitropoulos
PMCID: PMC1161560  PMID: 534498

Abstract

Carbon monoxide inhibited the removal of C-32 of dihydrolanosterol (I), but not of its metabolites 5 alpha-lanost-8-ene-3 beta,32-diol (II) and 3 beta-hydroxy-5 alpha-lanost-8-en-32-al (III). It appears therefore that cytochrome P-450 is a component of the enzyme system required to initiate oxidation of the 14 alpha-methyl group, but not of that responsible for the subsequent oxidation steps required for elimination of C-32 as formic acid. Non-radioactive compounds (II) and (III), when added to cell-free systems actively converting dihydrolanosterol into cholesterol, inhibited 14 alpha-demethylation measured by the rate of formation of labelled cholesterol from dihydro[1,7,15,22,26,30-14C]lanosterol or of labelled formic acid from dihydro[32-14C]lanosterol. However, neither compound (II) nor compound (III) accumulated radioactive label under these conditions. These observations could be attributed partly to inhibition of the initial oxidation of the 14 alpha-methyl group by compounds (II) and (III).

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Akhtar M., Alexander K., Boar R. B., McGhie J. F., Barton D. H. Chemical and enzymic studies on the characterization of intermediates during the removal of the 14alpha-methyl group in cholesterol biosynthesis. The use of 32-functionalized lanostane derivatives. Biochem J. 1978 Mar 1;169(3):449–463. doi: 10.1042/bj1690449b. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Akhtar M., Wilton D. C., Watkinson I. A., Rahimtula A. D. Substrate activation in pyridine nucleotide-linked reactions: illustrations from the steroid field. Proc R Soc Lond B Biol Sci. 1972 Feb 15;180(1059):167–177. doi: 10.1098/rspb.1972.0012. [DOI] [PubMed] [Google Scholar]
  3. CLAYTON R. B., BLOCH K. Biological synthesis of lanosterol and agnosterol. J Biol Chem. 1956 Jan;218(1):305–318. [PubMed] [Google Scholar]
  4. Fiecchi A., GAlli Kienle M., Scala A., Galli G., Grossi Paoletti E., Cattabeni F., Paoletti R. Hydrogen exchange and double bond formation in cholesterol biosynthesis. Proc R Soc Lond B Biol Sci. 1972 Feb 15;180(1059):147–165. doi: 10.1098/rspb.1972.0011. [DOI] [PubMed] [Google Scholar]
  5. Fried J., Dudowitz A., Brown J. W. Enzymatic conversion of 32-oxygenated delta-7-lanosterol derivatives and of delta-8(14)-4,4-dimethyl-cholestenol to cholesterol. Biochem Biophys Res Commun. 1968 Aug 13;32(3):568–574. doi: 10.1016/0006-291x(68)90701-8. [DOI] [PubMed] [Google Scholar]
  6. GAUTSCHI F., BLOCH K. Synthesis of isomeric 4,4-dimethylcholestenols and identification of a lanosterol metabolite. J Biol Chem. 1958 Dec;233(6):1343–1347. [PubMed] [Google Scholar]
  7. Gibbons G. F., Mitropoulos K. A. Effect of trans-1,4-bis(2-chlorobenzylaminomethyl) cyclohexane dihydrochloride and carbon monoxide on hepatic cholesterol biosynthesis from 4,4,-dimethyl sterols in vitro. Biochim Biophys Acta. 1975 Feb 20;380(2):270–281. doi: 10.1016/0005-2760(75)90013-2. [DOI] [PubMed] [Google Scholar]
  8. Gibbons G. F., Mitropoulos K. A., Pullinger C. R. Lanosterol 14alpha-demethylase. The metabolism of some potential intermediates by cell-free systems from rat liver. Biochem Biophys Res Commun. 1976 Apr 5;69(3):781–789. doi: 10.1016/0006-291x(76)90943-8. [DOI] [PubMed] [Google Scholar]
  9. Gibbons G. F., Mitropoulos K. A. The effect of carbon monoxide on the nature of the accumulated 4,4-dimethyl sterol precursors of cholesterol during its biosynthesis from (2-14C)mevalonic acid in vitro. Biochem J. 1973 Mar;132(3):439–448. doi: 10.1042/bj1320439. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Gibbons G. F., Mitropoulos K. A. The rôle of cytochrome P-450 in cholesterol biosynthesis. Eur J Biochem. 1973 Dec 3;40(1):267–273. doi: 10.1111/j.1432-1033.1973.tb03194.x. [DOI] [PubMed] [Google Scholar]
  11. Gibbons G. F. The metabolic sequence by which some 4,4-dimethyl sterols are converted into cholesterol. Biochem J. 1974 Oct;144(1):59–68. doi: 10.1042/bj1440059. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. KNAUSS H. J., PORTER J. W., WASSON G. The biosynthesis of mevalonic acid from 1-C14-acetate by a rat liver enzyme system. J Biol Chem. 1959 Nov;234:2835–2840. [PubMed] [Google Scholar]
  13. Kandutsch A. A., Chen H. W., Heiniger H. J. Biological activity of some oxygenated sterols. Science. 1978 Aug 11;201(4355):498–501. doi: 10.1126/science.663671. [DOI] [PubMed] [Google Scholar]
  14. LANGDON R. G., BLOCH K. The biosynthesis of squalene. J Biol Chem. 1953 Jan;200(1):129–134. [PubMed] [Google Scholar]
  15. Martin J. A., Huntoon S., Schroepfer G. J., Jr Enzymatic conversion of 14-alpha-methyl-cholest-7-en-3 beta, 15 zeta-diol to cholesterol. Biochem Biophys Res Commun. 1970;39(6):1170–1174. doi: 10.1016/0006-291x(70)90683-2. [DOI] [PubMed] [Google Scholar]
  16. Mitropoulos K. A., Gibbons G. F., Reeves B. E. Lanosterol 14alpha-demethylase. Similarity of the enzyme system from yeast and rat liver. Steroids. 1976 Jun;27(6):821–829. doi: 10.1016/0039-128x(76)90141-0. [DOI] [PubMed] [Google Scholar]
  17. Ono T., Bloch K. Solubilization and partial characterization of rat liver squalene epoxidase. J Biol Chem. 1975 Feb 25;250(4):1571–1579. [PubMed] [Google Scholar]
  18. Rodwell V. W., Nordstrom J. L., Mitschelen J. J. Regulation of HMG-CoA reductase. Adv Lipid Res. 1976;14:1–74. doi: 10.1016/b978-0-12-024914-5.50008-5. [DOI] [PubMed] [Google Scholar]
  19. Schroepfer G. J., Jr, Parish E. J., Chen H. W., Kandutsch A. A. Inhibition of sterol biosynthesis in L cells and mouse liver cells by 15-oxygenated sterols. J Biol Chem. 1977 Dec 25;252(24):8975–8980. [PubMed] [Google Scholar]
  20. Schroepfer G. J., Jr, Pascal R. A., Jr, Shaw R., Kandutsch A. A. Inhibition of sterol biosynthesis by 14alpha-hydroxymethyl sterols. Biochem Biophys Res Commun. 1978 Aug 14;83(3):1024–1031. doi: 10.1016/0006-291x(78)91498-5. [DOI] [PubMed] [Google Scholar]

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