Sphingolipid base metabolism. Stereospecific uptake of proton in the enzymatic conversion of sphinganine 1-phosphate to ethanolamine 1-phosphate

D-erythro-(2S, 3R)-Sphinganine 1-phosphate was incubated with rat liver microsomes in the presence of tritiated water. [3H]Ethanolamine 1-phosphate was isolated and converted, through a combination of enzymatic and chemical reactions, to [3H]glycine. The labeled glycine was incubated with D-amino acid oxidase, an enzyme which, in the catalysis of the conversion of glycine to glyoxylic acid, specifically removes the hydrogen in the S configuration at carbon atom 2 of glycine. Essentially complete retention of the labeled hydrogen occurred upon conversion to glyoxylic acid. The combined results indicate that the conversion of D-erythro-(2S,3R)-sphinganine 1-phosphate to palmitaldehyde and ethanolamine 1-phosphate, catalyzed by sphinganine-1-phosphate lyase of rat liver microsomes, proceeds with the stereospecific incorporation of 1 atom of solvent hydrogen into the R configuration of ethanolamine 1-phosphate.

Sphingolipid base metabolism. Sphinganine-1-phosphate lyase: identification of ethanolamine 1-phosphate as product

Ethanolamine 1-phosphate has been characterized as a product of the action of rat liver microsomal sphinganine 1-phosphate lyase on erythro-sphinganine 1-phosphate. The product was characterized by various forms of chromatography, gas-liquid chromatography-mass spectral analysis of appropriate derivatives, and by conversion to ethanolamine. The results of detailed studies of the mass spectral fragmentation of the tetra-trimethylsilyl derivative of ethanolamine 1-phosphate are also reported.

Mass spectral fragmentation of 5alpha-hydroxysteroids

The mass spectra of a number of C-4alpha- and C-4beta-alkylated cholestan-3beta, 5alpha-diols have been found to contain an intense ion at m/e 332. the corresponding 6beta-alkylated (R) cholestan-3beta, 5alpha-diols exhibit an abundant ion at m/e 331 + R. The mass spectra of cholestan-5alpha-ol and cholestan-3beta, 5alpha-diol also show an ion at m/e 332 which, however, is of relatively low abundance. The ion in question appears to arise from fragmentation processes which are characteristics of 5alpha-hydroxysteroids. A similar fragmentation has been found to occur in cases of C-4 and C-6beta-alkylated 5alpha-hysroxy-cholestan-3-ones. The results of isotopic labeling, high resolution and metastable ion defocusing studies are discussed in terms of the origin of several of the ions in the spectra of the various compounds.

Enzymatic conversion of 5alpha-cholesta-7, 14-dien-3beta-ol to 5alpha-cholesta-8, 14-dien-3beta-ol

5alpha-Cholesta-7, 14-dien-3beta-ol, previously shown to be efficiently converted to cholesterol upon incubation with rat liver homogenate preparations under aerobic conditions, has been studied as to its possible conversion to 5alpha-cholesta-8, 14-dien-3beta-ol. Efficient conversion was observed upon incubation in the presence of washed mictosomes of rat liver under anaerobic conditions. This observation is of importance in consideration of possible metabolic pathways in the biosythesis of cholesterol.

Chemical synthesis, spectral properties, and chromatography of 4alpha-methyl and 4beta-methyl isomers of (24R)-24-ethyl-5alpha-cholestan-3beta-ol and (24S)-24-ethyl-cholesta-5,22-dien-3beta-ol

Described herein are chemical syntheses of the following compounds: 4-methyl-(24S)-24-ethyl-cholesta-4,22-dien-3-one, 4,4-dimethyl-(24S)-24-ethyl-cholesta-5,22-dien-3-one, 4beta-methyl-(24R)-24-ethyl-5alpha-cholestan-3beta-ol, 4alpha-methyl-(24R)-24-ethyl-5alpha-cholestan-3beta-ol, 4alpha-methyl-(24S)-24-ethyl-5alpha-cholest-22-en-3beta-ol, 4-methyl-6beta-bromo-(24S)-24-ethyl-cholesta-4,22-dien-3-one, 4alpha-methyl-(24S)-24-ethyl-cholesta-5,22-dien-3beta-ol, 4alpha,5alpha-epoxy-(24S)-24-ethyl-cholesta-4,22-dien-3beta-yl acetate, 4beta-methyl-(24S)-24-ethyl-cholest-22-en-3beta,5alpha-diol, 4beta-methyl-5alpha-hydroxy-(24S)-24-ethyl-cholest-22-en-3beta-yl acetate, 4beta-methyl-(24S)-24-ethyl-cholesta-5,22-dien-3beta-yl acetate and 4beta-methyl-(24S)-24-ethyl-cholesta-5,22-dien-3beta-ol. Chromatographic, nuclear magnetic resonance, and mass spectral data are presented for the compounds under consideration.

Inhibition of enzymatic reduction of delta 14-double bond of 5 alpha-cholesta-8,14-dien-3 beta-ol and 5 alpha-cholesta-7,14-dien-3 beta-ol by AY-9944

AY-994 (trans-1,4-bis-(2-chlorobenzyl-aminomethyl) cyclohexane dihydrochloride), a potent inhibitor of the enzymatic reduction of the delta 7-double bond of delta 5,7-sterols, has been shown to inhibit, at higher concentrations (10-4 M), the enzymatic reduction of the delta 14-double bond of cholesta-8,14-dien-3 beta-ol and cholesta-7,14-dien-3 beta-ol.