Steric effects at C-20 and C-24 on the metabolism of sterols by Tetrahymena pyriformis.

A novel Tetrahymena thermophila sterol C-22 desaturase belongs to the fatty acid hydroxylase/desaturase superfamily

“…Our bioinformatic analysis of the different enzymes from the FAHD superfamily enabled the identification of an extra histidine cluster that was only described in the stearoyl-CoA desaturase family ( 29 ), thus increasing the number of clusters from three ( 27 ) to four in each family necessary for the heme coordination in the active site. The analysis of C22 sterol/acylamide-delta-3(E) desaturase family also shows a conserved arginine in the sequences from bacteria and fungus not present in ciliates and Viridiplantae that could explain, at least partially, the different substrate preferences of the two enzymes classes ( 4 , 41 ). Although single amino acid substitution has shown to change the substrate specificity for different fatty acids in FAHD ( 42 ), the change of specificity between two highly different substrates (sterols versus sphingolipids) would surely imply several substitutions as well as structural changes in the enzymes, not yet described.…”

Widespread Sterol Methyltransferase Participates in the Biosynthesis of Both C4α- and C4β-Methyl Sterols

“…The isotopic patterns were deconvoluted with Excel spreadsheets to calculate the positions and extents of the sterols’ isotope labeling . Keto sterols generated in the reactions to produce substances for NMR analysis were reduced by overnight incubation with sodium borohydride in isopropanol solution, as previously reported …”

“…35 Keto sterols generated in the reactions to produce substances for NMR analysis were reduced by overnight incubation with sodium borohydride in isopropanol solution, as previously reported. 36 Phylogenic Tree Reconstruction. The methyltransferase domain (PFAM13649) was used to search STRM candidates across all eukaryotes and bacteria by HMMER search.…”

A Concise Account of Various Approaches for Stereoselective Construction of the C-20(H) Stereogenic Center in Steroid Side Chain

“…Koreeda and co-workers reported that 20- epi -cholesterol 32 with C­(20 S ) stereochemistry showed significant in vitro inhibitory activity for the conversion of cholesterol to 3β-hydroxypregn-5-en-20-one (pregnenolone). Similarly, the naturally occurring halosterol 33 , in which the side chain has been shortened by one methylene (CH 2 ) group, possesses unnatural configuration at C-20 …”