Lanosterol

About: Lanosterol is a research topic. Over the lifetime, 1239 publications have been published within this topic receiving 36737 citations. The topic is also known as: (3β)-lanosta-8,24-dien-3-ol & (3β,20R)-lanosta-8,24-dien-3-ol.

Cholesterol biosynthesis from lanosterol: differential inhibition of sterol delta 8-isomerase and other lanosterol-converting enzymes by tamoxifen.

Abstract: The fact that administration of tamoxifen (Tam) to humans and laboratory animals (e.g., rats and monkeys) results in both a drastic reduction in cholesterol and a marked accumulation of certain sterol intermediates in their serum led us to undertake more direct biochemical studies on the mechanism of Tam's inhibitory action on the cholesterogenic enzymes. Of the five rat hepatic lanosterol-converting enzymes examined, the enzyme most sensitive to inhibition by Tam was sterol delta 8-isomerase (delta 8-SI) (a 208-fold inhibition relative to lanosterol 14 alpha-methyl demethylase), followed by sterol delta 24-reductase (13-fold) and sterol delta 14-reductase (5.2-fold). The inhibition patterns of all four affected enzymes were found to be noncompetitive, despite widely different inhibition constants (Ki) of 0.21 to 23.5 microM. The inhibitory activity of Tam on delta 8-SI was not affected by detergent-mediated solubilization of the microsomes. In Chinese hamster ovary cells, inhibition of delta 8-SI activity (IC50 = 0.15 microM) was paralleled by a decreased rate of [14C]-mevalonate incorporation into cholesterol (IC50 = 0.70 microM). Our results should provide more insight into an underlying mechanism of Tam's cardioprotective role by interfering the operation of the pathway of cholesterol biosynthesis from lanosterol in mammals.

In vitro effects of oxygenated lanosterol derivatives on cholesterol biosynthesis from 24,25-dihydrolanosterol

Abstract: The effects of oxygenated lanosterol derivatives (1-27, 5μM) including 32-oxygenated lanosterol derivatives on cholesterol biosyntheiss from [24, 25-3H2]-24, 25-dihydrolanosterol (18μM) were tested in 10000×g supernatant (S-10) fraction of rat liver homogenate. Among the derivatives, 7-oxolanost-8-en-3β-ol (7-oxo-DHL), 3β-acetoxylanost-8-en-7-one (7-oxo-DHL-3-OAc), and 7-oxolanosta-5, 8, 11-trien-3β-ol were highly active in depression cholesterol biosynthesis from 24, 25-dyhydrolanosterol. The inhibitory activities of these derivatives on cholesterol synthesis are discussed on the basis of the position and stereochemistry of the oxygen functional groups on the sterol nucleus. The effect of aphidicolin on cholesterol synthesis was also compared with that of 7-oxo-DHL.

Sterol 14alpha-demethylase activity in Streptomyces coelicolor A3(2) is associated with an unusual member of the CYP51 gene family.

Abstract: The annotation of the genome sequence of Streptomyces coelicolor A3(2) revealed a cytochrome P450 (CYP) resembling various sterol 14alpha-demethylases (CYP51). The putative CYP open reading frame (SC7E4.20) was cloned with a tetrahistidine tag appended to the C-terminus and expressed in Escherichia coli. Protein purified to electrophoretic homogeneity was observed to bind the 14-methylated sterols lanosterol and 24-methylene-24,25-dihydrolanosterol (24-MDL). Reconstitution experiments with E. coli reductase partners confirmed activity in 14alpha-demethylation for 24-MDL, but not lanosterol. An S. coelicolor A3(2) mutant containing a transposon insertion in the CYP51 gene, which will abolish synthesis of the functional haemoprotein, was isolated as a viable strain, the first time a CYP51 has been identified as non-essential. The role of this CYP in bacteria is intriguing. No sterol product was detected in non-saponifiable cell extracts of the parent S. coelicolor A3(2) strain or of the mutant. S. coelicolor A3(2) CYP51 contains very few of the conserved CYP51 residues and, even though it can catalyse 14alpha-demethylation, it probably has another function in Streptomyces. We propose that it is a member of a new CYP51 subfamily.