570-89-8Relevant academic research and scientific papers
Isomerization, but not oxidation, is suppressed by a single point mutation, E361Q, in the reaction catalyzed by cholesterol oxidase
Sampson, Nicole S.,Kass, Ignatius J.
, p. 855 - 862 (2007/10/03)
The putative active site base of cholesterol oxidase from Streptomyces has been removed by site-directed mutagenesis and the mutant enzyme characterized. When glutamate-361 is mutated to a glutamine, the isomerization chemistry catalyzed by cholesterol oxidase is suppressed and the intermediate cholest-5-ene-3-one is isolated. The specific activity for oxidation is 20-fold slower than the wild-type reaction, though the specific activity for isomerization is 10000-fold slower. Furthermore, incubation of cholest-5-ene-3-one with the E361Q cholesterol oxidase resulted in the production of cholest-4-ene-6β-hydroperoxy-3-one (6%), cholest-4-ene-3,6-dione (32%), cholest-4-ene-6β-ol-3-one (36%), and cholest-4-ene-6α-hydroperoxy-3-one/cholest-4-ene-6α-ol-3-one (13%), in addition to cholest-4-ene-3-one (13%). Measurement of reaction stoichiometry eliminated the possibility that H2O2 or the C4a-hydroperoxy flavin was the oxygenation agent. It is proposed that cholest-4-ene-6-hydroperoxy-3-one is the product of radical chain autoxidation and that cholest-4-ene-3,6-dione and cholest-4-ene-6-ol-3-one are decomposition products of the hydroperoxy steroid radical. The characterization of the E361Q mutant chemistry has illuminated the importance of intermediate sequestration in enzyme catalysis. The mutant enzyme will be used to obtain information about the structure of the enzyme in the presence of the reaction intermediate. Moreover, the altered activity of E361Q cholesterol oxidase will facilitate its application in studies of cell membranes.
Stereospecific oxidation of 3β-hydroxysteroids by persolvent fermentation with Pseudomonas sp. ST-200
Aono, Rikizo,Doukyu, Noriyuki
, p. 1146 - 1151 (2007/10/03)
Pseudomonas sp. strain ST-200 isolated from a humus soil effectively oxidizes cholesterol dissolved in organic solvents but not that suspended in the growth medium. The organism does not assimilate cholesterol. This organism oxidized a variety of 5α- or 5-ene-steroids dissolved in organic solvent. First, the 3β-OH group was oxidized to a ketone group. The 3α-OH group was scarcely oxidized. Successively, C-6 position of 5-ene-steroids was hydroxylated, and a double bond of 5-ene-steroids was transferred from Δ5 to Δ4. Then, the 6-OH group was oxidized to a ketone group. Persolvent fermentation with ST-200 would provide an effective, convenient, and stereospecific method to oxidize the C-3 and C-6 positions of steroids.
Allylic Hydroperoxides Formed by Singlet Oxygenation of Cholest-5-en-3-one
Dang, Hai-Shan,Davies, Alwyn G.,Schiesser, Carl H.
, p. 789 - 794 (2007/10/02)
Cholest-5-en-3-one (I) reacts with singlet oxygen to give the hemiperketal (II) (ca. 55percent), the epimeric 6β- and 6α-hydroperoxides (III) and (IV) (ca. 30 and 8percent respectively), and the dione (V) (ca 7percent).The hemiperketal (II) does not undergo an allylic rearrangement in solution, but the hydroperoxides (III) and (IV) epimerise by a radical chain mechanism. .Stereochemical problems connected with this system have been probed by carrying out parallel experiments and molecular mechanics calculations on the corresponding derivatives of methyloctahydronaphthalenone as model compounds.
Catalytic Oxygenation of Cholesterol with a Platinum Catalyst under Moderate Pressure of Oxygen
Sakamaki, Hiroshi,Take, Masa-aki,Akihisa, Toshihiro,Matsumoto, Taro,Ichinohe, Yoshiyuki
, p. 3023 - 3025 (2007/10/02)
The catalytic oxigenation of cholesterol 1 with a platinum black catalyst under moderate pressure (20-25 atm) of oxygen yielded eleven oxidation products, 3-13a.The reaction pathway of the catalytic oxygenation is discussed on the basis of the results for several reaction conditions.
