Inhibition of the conversion of cholesterol to pregnenolone in bovine adrenocortical preparations

Burstein, Shlomo; Letourneux, Yves; Kimball, Howard L.; Gut, Marcel

doi:10.1016/0039-128x(76)90057-x

Cited by 12 publications

(6 citation statements)

References 40 publications

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“…Collectively, the active site amino acid residues form a cavity whose shape is in good agreement with previous studies on CYP11A1 substrate specificity. The enzyme active site was shown to have strict requirements for the planarity of the sterol backbone, extra space beyond the 3␤-hydroxyl and aliphatic tail, and limited space at carbon atoms 4 -6 and 17 (13)(14)(15)(16)(17)(18)(19)(20)(21)(22).…”

Section: Resultsmentioning

confidence: 99%

Structural Basis for Three-step Sequential Catalysis by the Cholesterol Side Chain Cleavage Enzyme CYP11A1

Mast

Annalora

Lodowski

et al. 2011

Journal of Biological Chemistry

125

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Mitochondrial cytochrome P450 11A1 (CYP11A1 or P450 11A1) is the only known enzyme that cleaves the side chain of cholesterol, yielding pregnenolone, the precursor of all steroid hormones. Pregnenolone is formed via three sequential monooxygenation reactions that involve the progressive production of 22R-hydroxycholesterol (22HC) and 20␣,22R-dihydroxycholesterol, followed by the cleavage of the C20-C22 bond. Herein, we present the 2.5-Å crystal structure of CYP11A1 in complex with the first reaction intermediate, 22HC. The active site cavity in CYP11A1 represents a long curved tube that extends from the protein surface to the heme group, the site of catalysis. 22HC occupies two-thirds of the cavity with the 22R-hydroxyl group nearest the heme, 2.56 Å from the iron. The space at the entrance to the active site is not taken up by 22HC but filled with ordered water molecules. The network formed by these water molecules allows the "soft" recognition of the 22HC 3␤-hydroxyl. Such a mode of 22HC binding suggests shuttling of the sterol intermediates between the active site entrance and the heme group during the three-step reaction. Translational freedom of 22HC and torsional motion of its aliphatic tail are supported by solution studies. The CYP11A1-22HC co-complex also provides insight into the structural basis of the strict substrate specificity and high catalytic efficiency of the enzyme and highlights conserved structural motifs involved in redox partner interactions by mitochondrial P450s.

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Section: Resultsmentioning

confidence: 99%

Structural Basis for Three-step Sequential Catalysis by the Cholesterol Side Chain Cleavage Enzyme CYP11A1

Mast

Annalora

Lodowski

et al. 2011

Journal of Biological Chemistry

125

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“…Although these conflicting results were both obtained with highly purified enzymes, the experimental conditions differed in several respects. Burstein et al [50] have studied the effects of many cholesterol analogues on the formation of [14C]pregnenolone from ['4C]cholesterol in crude adrenal mitochondria1 acetone powder extracts. Since an indeterminate number of the compounds tested by Burstein et al [50] were also substrates, it is somewhat difficult to interpret their findings conclusively.…”

Section: Steroid Addedmentioning

confidence: 99%

“…Burstein et al [50] have studied the effects of many cholesterol analogues on the formation of [14C]pregnenolone from ['4C]cholesterol in crude adrenal mitochondria1 acetone powder extracts. Since an indeterminate number of the compounds tested by Burstein et al [50] were also substrates, it is somewhat difficult to interpret their findings conclusively. Nevertheless, these authors found 20-isocholesterol to be a considerably more potent inhibitor of the enzymatic process than is indicated by our experimen ts.…”

Section: Steroid Addedmentioning

confidence: 99%

Biosynthesis of Pregnenolone from Cholesterol by Mitochondrial Enzymes of Bovine Adrenal Cortex. The Question of the Participation of the 20(22)-Olefins and 20,22-Epoxides of Cholesterol

et al. 1978

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The two isomeric 20(22)-olefins and the four isomeric 20,22-epoxides of cholesterol have been examined as possible intermediates in the conversion of cholesterol to pregnenolone both by crude extracts of acetone-dried bovine adrenal cortex mitochondria, and by a partially purified cytochrome P-450 specific for the side chain cleavage ( P -4 5 0~~~) .The quantities of pregnenolone (measured by radioimmunoassay) formed from these putative intermediates and from cholesterol, (2057-20-hydroxycholesterol, (22R)-22-hydroxycholesterol, and (20R,22R)-20,22-dihydroxycholesterol have been compared. In both crude and purified systems, the conversion of the monohydroxycholesterols is somewhat more rapid than that of cholesterol. However, the dihydroxycholesterol is a very much more efficient precursor of pregnenolone. Whereas small amounts of pregnenolone were formed from the four 20,22-epoxycholesteroIs, and slightly larger amounts from the two 20(22)-didehydrocholesterols in the crude enzyme systems, almost no conversion of these six compounds was observed with the purified system containing cytochrome P-45Oscc, adrenodoxin, adrenodoxin reductase, and an NADPH-generating system. It is concluded that the olefins and epoxides are not obligatory intermediates in the conversion of cholesterol to pregnenolone, and the conversions of cholesterol olefins and epoxides observed by us and by others may reflect the presence of extraneous enzymes such as double bond reductases and epoxide hydratases which are unrelated to pregnenolone biosynthesis. The relative effectiveness of the cholesterol olefins and epoxides, as well as 20-isocholesterol in inhibiting the formation of pregnenolone from [4-14C]cholesterol has been determined. The compounds which have the same configuration as cholesterol at C-20 are more potent inhibitors of this conversion than the olefins in which the C-21, C-20, C-22, C-23 carbon system is planar, or than those compounds which have the opposite configuration to cholesterol at C-20 (i.e. 20-isocholesterol, (20S,22S)-20,22-epoxycholesterol and (20S,22R)-20,22-epoxycholesterol). The enzyme appears to be more fastidious in its steric requirement at C-20 than at C-22. Since the olefins and epoxides are stereochemically rigidified around the C-20 to C-22 bond, these inhibitor studies suggest that the natural conformation of cholesterol on the side chain cleavage enzyme system is such that the side chain is fully extended and thus closely resembles the conformation of cholesterol in the crystal state. Abbreviations. The following abbreviations are used : cytochrome P-45OSCC, a highly purified bovine adrenal cortex mitochondrial cytochrome P-450 that cleaves the side chain of cholesterol to pregnenolone and is inactive in the 11 P-hydroxylation reaction; pregnenolone, 3a-hydroxypregn-5-en-20-one; cyanoketone, 2cc-cyEnzymes. Adrenodoxin reductase (EC 1.6.7.1); glucose-6-phosphate dehydrogenase (EC 1 .I. 1.49).

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“…The a,/3 epimers were separated by chromatography and reduction of nitrile a epimer (mp: 180°C; tH-NMR spectrum showed 8 = 3.10 (dd; 1 H; J7/3-6 = 5, J7/3-4 = 2; H-6)) was achieved to give amine II. Biologically active [8,9] 22R-aminocholesterol (compound III) was prepared according to Burnstein et al [10].…”

Section: Introductionmentioning

confidence: 99%

“…Biologically active [8,9] 22R-aminocholesterol (compound III) was prepared according to Burnstein et al [10].…”

Section: Chemistrymentioning

confidence: 99%

Amino- and aminomethylcholesterol derivatives with fungicidal acitivity

Elkihel¹

1994

FEMS Microbiology Letters

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Among a series of aminocholesterol derivatives synthesized, 7-aminocholesterol is the strongest inhibitor of yeast cell growth. Using sterol auxotrophic mutant strains, we showed that this compound inhibits cell proliferation by interfering with ergosterol biosynthesis. The sterol pattern of treated cells revealed that 7-aminocholesterol inhibits A 8 ~ A7-sterol isomerase and A14-sterol reductase as morpholine inhibitors. However, the novel feature of this compound is a strong cytotoxicity to yeast.

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Inhibition of the conversion of cholesterol to pregnenolone in bovine adrenocortical preparations

Cited by 12 publications

References 40 publications

Structural Basis for Three-step Sequential Catalysis by the Cholesterol Side Chain Cleavage Enzyme CYP11A1

Structural Basis for Three-step Sequential Catalysis by the Cholesterol Side Chain Cleavage Enzyme CYP11A1

Biosynthesis of Pregnenolone from Cholesterol by Mitochondrial Enzymes of Bovine Adrenal Cortex. The Question of the Participation of the 20(22)-Olefins and 20,22-Epoxides of Cholesterol

Amino- and aminomethylcholesterol derivatives with fungicidal acitivity

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