pathway prior to lanosterol synthesis is commonly referred ..

T1 - Lack of squalene and lanosterol synthesis by the perfused human placenta at term

Formation of the C Ring in the Lanosterol Biosynthesis ..

A mechanism is proposed for the formation of the C and D rings of lanosterol from squalene on the basis of density functional calculations of a model cyclopentylcarbinyl carbocation. The mechanism involves the ring expansion of the cyclopentylcarbinyl carbocation to the six-membered ring C in concert with the formation of the D ring. The mechanism does not involve a violation of Markovnikov's rule as the earlier proposed mechanism does for the formation of rings C and D.

Akashi, Oxidation of Alcohols to Aldehydes by Reagents Derived from Chromyl Chloride,

the biosynthesis of lanosterol from squalene

Classical pathway from acetate to isoprene units. Condensation of three acetate moieties yields HMG‐CoA. Reduction of HMG‐CoA to mevalonate by HMG‐CoA reductase is the rate‐limiting step in cholesterol biosynthesis. Phosphorylation and decarboxylation of mevalonate yields IPP and DMAPP. Small, straight arrows indicate atoms where chemistry occurs in subsequent step; curved arrows show electron flow during decarboxylation step.

The Biosynthesis of Squalene, Lanosterol, and …

N2 - Three human term placentas were perfused in vitro with 1.6-2.4 mCi of carbon-14 labelled sodium acetate for 90-120 min and attempts were made to isolate from the placentas and perfusates labelled squalene, lanosterol, cholesterol, pregnenolone and progesterone. All carbon-14 labelled material was dissociated from the squatene, cholesterol, pregnenolone and progesterone isolated from the three placentas and three perfusates. The same was found with regard to lanosterol isolated from three perfusates and one placenta. Minute amounts of radiochemically homogeneous lanosterol were isolated from the second placenta, whereas the evidence was inconclusive in the case of minute amounts of lanosterol-like material recovered from the third placenta. It is concluded that little, if any, squalene, lanosterol and cholesterol are synthesized by the human placenta perfused at term.

SQUALENE AND LANOSTEROL SYNTHESIS IN THE …


Synthesis of cholesterol from lanosterol

T1 - Synthesis and inhibition studies of sulfur-substituted squalene oxide analogues as mechanism-based inhibitors of 2,3-oxidosqualene-lanosterol cyclase

Squalene is a natural 30-carbon organic ..

Synthesis of cholesterol from lanosterol. The DHCR24 (Δ24‐reductase) enzyme can reduce all the sterols shown on the left side. The key carbon atoms are numbered in the lanosterol structure (top), and all carbon atoms of cholesterol are numbered (bottom).

and is a precursor for synthesis of all ..

AB - Three human term placentas were perfused in vitro with 1.6-2.4 mCi of carbon-14 labelled sodium acetate for 90-120 min and attempts were made to isolate from the placentas and perfusates labelled squalene, lanosterol, cholesterol, pregnenolone and progesterone. All carbon-14 labelled material was dissociated from the squatene, cholesterol, pregnenolone and progesterone isolated from the three placentas and three perfusates. The same was found with regard to lanosterol isolated from three perfusates and one placenta. Minute amounts of radiochemically homogeneous lanosterol were isolated from the second placenta, whereas the evidence was inconclusive in the case of minute amounts of lanosterol-like material recovered from the third placenta. It is concluded that little, if any, squalene, lanosterol and cholesterol are synthesized by the human placenta perfused at term.