Biosynthesis of estrogens. Assignment of the chemical shift of the 19-pro-chiral hydrogen atoms of a 19-hydroxy precursor

Caspi, Eliahu; Santaniello, Enzo; Patel, Kaushalendra; Arunachalam, T.; Eck, Charles R.

doi:10.1021/ja00484a060

Cited by 11 publications

(6 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This requirement for the conversion of an alcohol into an aldehydic group (2 → 4) was rationalized by assuming the involvement of a second hydroxylation reaction producing a gem diol intermediate (3). In the latter conversion the new hydroxyl group was inserted into the H Re position and then stereospecifically removed in the next dehydration reaction producing 4 [9,[12][13][14][15] …”

Section: Historic Backgroundmentioning

confidence: 99%

A review of mechanistic studies on aromatase (CYP19) and 17α-hydroxylase-17,20-lyase (CYP17)

Akhtar

Wright

Lee-Robichaud

2011

The Journal of Steroid Biochemistry and Molecular Biology

105

View full text Add to dashboard Cite

Section: Historic Backgroundmentioning

confidence: 99%

A review of mechanistic studies on aromatase (CYP19) and 17α-hydroxylase-17,20-lyase (CYP17)

Akhtar

Wright

Lee-Robichaud

2011

The Journal of Steroid Biochemistry and Molecular Biology

105

View full text Add to dashboard Cite

“…According to Scheme 1, the first hydroxylation occurs at C-19 to produce 1 9-hydroxy-4-androstene-3,17-dione (II) (Meyer, 1955); this, in the second oxidation step, is converted to the corresponding 1 9-aldehyde (IV), presumably through the intermediacy of the gem-diol (III) (Akhtar & Skinner, 1968). The mechanistic details and absolute stereochemistry of the second oxidation reaction, (II) to (IV), have been elucidated by a number of independent approaches (Arigoni et al, 1975;Osawa et al, 1975;Caspi et al, 1978). The.…”

mentioning

confidence: 99%

Mechanistic studies on C-19 demethylation in oestrogen biosynthesis

Akhtar

Calder

Corina

et al. 1982

Biochemical Journal

279

220

View full text Add to dashboard Cite

Mechanistic aspects of the biosynthesis of oestrogen have been studied with a microsomal preparation from full-term human placenta. The overall transformation, termed the aromatization process, involves three steps using O2 and NADPH, in which the C-19 methyl group of an androgen is oxidised to formic acid with concomitant production of the aromatic ring of oestrogen: [Formula: see text] To study the mechanism of this process in terms of the involvement of the oxygen atoms, a number of labelled precursors were synthesized. Notable amongst these were 19-hydroxy-4-androstene-3,17-dione (II) and 19-oxo-4-androstene-3,17-dione (IV) in which the C-19 was labelled with2H in addition to18O. In order to follow the fate of the labelled atoms at C-19 of (II) and (IV) during the aromatization, the formic acid released from C-19 was benzylated and analysed by mass spectrometry. Experimental procedures were devised to minimize the exchange of oxygen atoms in substrates and product with oxygens of the medium. In the conversion of the 19-[18O] compounds of types (II) and (IV) into 3-hydroxy-1,3,5-(10)-oestratriene-17-one (V, oestrone), it was found that the formic acid from C-19 retained the original substrate oxygen. When the equivalent16O substrates were aromatized under18O2, the formic acid from both substrates contained one atom of18O. It is argued that in the conversion of the 19-hydroxy compound (II) into the 19-oxo compound (IV), the C-19 oxygen of the former remains intact and that one atom of oxygen from O2 is incorporated into formic acid during the conversion of the 19-oxo compound (IV) into oestrogen. This conclusion was further substantiated by demonstrating that in the aromatization of 4-androstene-3,17-dione (I), both the oxygen atoms in the formic acid originated from molecular oxygen. 10β-Hydroxy-4-oestrene-3,17-dione formate, a possible intermediate in the aromatization, was synthesized and shown not to be converted into oestrogen. In the light of the cumulative evidence available to date, stereochemical aspects of the conversion of the 19-hydroxy compound (II) into the 19-oxo compound (IV), and mechanistic features of the C-10–C-19 bond cleavage step during the conversion of the 19-oxo compound (IV) into oestrogen are discussed.

show abstract

“…The conversion of androgens into oestrogens (1-4, Scheme 1) is catalysed by cytochrome P-450 aromatase ([1] and references cited therein) and occurs through the participation of three sequential oxidation reactions at C-19, each requiring 1 mol of NADPH and 1 mol of 02 [2][3][4][5]. We have extensively studied the mechanism of action of the enzyme, and the salient feature of our findings [1,[3][4][5], which have received support from the studies of other groups [6][7][8], are summarized in the sequence of Scheme 1. This subject has recently been reviewed [5].…”

Section: Introductionmentioning

confidence: 55%

“…A maximum titre was given by adding excess inhibitor (25 ,UM for both cases) to fully saturate the enzyme. (b) The same procedure was repeated for azidosteroid, except that the final concentrations in the cuvette were 2.0, 3.0 The illustration shows the formation of co-ordinate bonds between the nitrogen of the azidosteroid (5) or the sulphur of the thiomethylsteroid (6) and the iron in the haem b prosthetic group (7) of aromatase.…”

Section: Resultsmentioning

confidence: 99%

‘Slow-binding’ sixth-ligand inhibitors of cytochrome P-450 aromatase. Studies with 19-thiomethyl- and 19-azido-androstenedione

Wright

Slatcher

Akhtar

1991

Biochemical Journal

View full text Add to dashboard Cite

The progress curves for the inhibition of aromatase by 19-thiomethylandrostenedione and 19-azidoandrostenedione were found to be non-linear where the extent of inhibition increased with time. Further experiments enabled these compounds to be classified as 'slow-binding' inhibitors of aromatase. The phenomenon was attributed to the formation of an initial E.I complex that rearranged to another species (E.I*) in which the interaction between the enzyme and inhibitor had been maximized, giving rise to tighter binding. When 19-thiomethylandrostenedione was used as the inhibitor the t0.5 (half-time) for the dissociation of E.I* was calculated to be 12.6 min with Ki and Ki* values of 2.4 and 1.4 nM respectively. In the case of 19-azidoandrostenedione, the two separate dissociation constants were not determined, and a single Ki value of 5 nM was obtained. The conclusions drawn from kinetic studies were confirmed by absorption spectrometry, when time-dependent formation of complexes between aromatase and either 19-thiomethylandrostenedione or 19-azidoandrostenedione were observed by the formation of 'Type II' spectra. The two complexes respectively had maxima at 429 and 418 nm. The spectral data suggested that the two inhibitors interact with the haem iron of aromatase, forming hexaco-ordinated species for which structural models are presented.

show abstract

Biosynthesis of estrogens. Assignment of the chemical shift of the 19-pro-chiral hydrogen atoms of a 19-hydroxy precursor

Cited by 11 publications

References 2 publications

A review of mechanistic studies on aromatase (CYP19) and 17α-hydroxylase-17,20-lyase (CYP17)

A review of mechanistic studies on aromatase (CYP19) and 17α-hydroxylase-17,20-lyase (CYP17)

Mechanistic studies on C-19 demethylation in oestrogen biosynthesis

‘Slow-binding’ sixth-ligand inhibitors of cytochrome P-450 aromatase. Studies with 19-thiomethyl- and 19-azido-androstenedione

Contact Info

Product

Resources

About