Stereochemistry of dehydrogenation catalyzed by Acyl-CoA oxidase

The stereochemical course of dehydrogenation catalyzed by acyl-CoA oxidase was investigated using the enzymes from rat liver peroxisomes and Candida lipolytica. Stearoyl-CoA and nonanoyl-CoA, stereospecifically labeled with deuterium at either C-2 or C-3, were incubated with the enzyme, the products were converted to methyl esters and their deuterium contents were measured by gas chromatography-mass spectrometry. The results suggested that acyl-CoA oxidase-catalyzed dehydrogenation occurred by anti-elimination of the pro 2R and pro-3R hydrogens of acyl-CoA.

Substrate control of termination of fatty acid biosynthesis by fatty acid synthetase from Brevibacterium ammoniagenes

The pattern of fatty acids produced by the fatty acid synthetase complex of Brevibacterium ammoniagenes under several conditions was examined. The fatty acid synthetase obtained from B. ammoniagenes produced oleic acid as well as saturated fatty acids (palmitic and stearic acids). The relative proportions of palmitic to stearic acids varied over a wide range. Such alterations were dependent on the malonyl-CoA concentration and the ratio of acetyl-CoA to malonyl-CoA concentrations. At malonyl-CoA concentrations higher than 100 microM, stearic acid accounted for more than 90% of the saturated fatty acids and the pattern of fatty acid synthesized was independent on the ratio of acetyl-CoA to malonyl-CoA. At malonyl-CoA concentrations lower than 100 microM, raising the acetyl-CoA/malonyl-CoA ratio increased the percentage of palmitic acid. However, the proportion of oleic acid produced remained almost constant under all conditions tested.

Stereochemical course of enoyl reduction catalyzed by fatty acid synthetase. Stereochemistry of hydrogen incorporation from reduced pyridine nucleotide

The stereochemical course of the enoyl reduction catalyzed by fatty acid synthetase was investigated using the enzymes from rat liver and Brevibacterium ammoniagenes. Deuterium-labeled fatty acids were synthesized by incubating the synthetases with either 4R-[4-2H1]- or 4S-[4-2H1]NADPH. The deuterium-labeled fatty acids thus produced were subjected to the action of a stereospecific enzyme, acyl-CoA oxidase. The deuterium-labeled fatty acids and 2,3-dehydroacyl thioesters, the products of acyl-CoA oxidase, were methylated and analyed for deuterium content by gas chromatography-mass spectrometry. These experiments provided information to determine the configuration at the C-3 position of fatty acids formed by fatty acid synthetases. The results suggested that the stereochemistry of hydrogen (as hydride) incorporation from reduced pyridine nucleotides during enoyl reduction was different between rat liver and B. ammoniagenes synthetases: the enoyl reduction of rat liver enzyme involved the re-attack of hydride and that of B. ammoniagenes enzyme involved the si-attack of hydride.

Incorporation of hydrogen atoms from deuterated water and stereospecifically deuterium-labeled nicotin amide nucleotides into fatty acids with the Escherichia coli fatty acid synthetase system

The mechanism of hydrogen incorporation into fatty acids was investigated with intact Escherichia coli cells, a crude enzyme preparation and purified reductases of fatty acid synthetase system. The distributions of deuterium atoms incorporated into fatty acids from 2H2O and stereospecifically deuterium-labeled NADPH or NADH were determined by mass spectrometry. When E. coli was grown in 2H2O, almost every hydrogen atom of cellular fatty acids was incorporated from the medium. When fatty acids were synthesized from acetyl-CoA, malonyl-CoA and NADPH in the presence of a crude enzyme preparation of either E. coli or Bacillus subtilis, almost every hydrogen atom was also incorporated from the medium. In contrast to these results, purified beta-ketoacyl acyl carrier reductase directly transferred the HB hydrogen of NADPH to beta-ketoacyl acyl carrier protein, and purified enoyl acyl carrier protein reductase also transferred the HB hydrogen of NADPH and NADH directly to enoyl acyl carrier protein. In the crude enzyme preparation of E. coli, we found high activities which exchanged the HB hydrogen of NADPH with the deuterium of 2h2o. the conflicting results of the origin of hydrogen atoms of fatty acids mentioned above are explained by the presence of enzymes, which catalyzed the rapid exchange of NADPH with the deterium of 2H2O prior to the reaction of fatty acid synthetase.

Ionic strength dependent enzyme activities of elastase

Peptidase and esterase activities of elastase were each altered separately by the ionic strength of the buffer used. The esterase activity is exerted in a lower ionic strength medium where the peptidase activity is not detected.

Thermal regulation of fatty acid synthetase from Brevibacterium ammoniagenes

The fatty acid composition of Brevibacterium ammoniagenes was affected by the temperature of growth. As the growth temperature was lowered, the proportion of unsaturated fatty acids increased. The fatty acid synthetase obtained from B. ammoniagense produced oleic acid as well as saturated fatty acids. The ratio of unsaturated to saturated fatty acids synthesized by this enzyme in vitro was dependent on the temperature of the enzyme reaction but not on the growth temperature of B. ammoniagenes from which the enzyme was prepared. These results suggest that the changes of composition in cellular fatty acids reflect the temperature dependence of the fatty acid synthetase.

Formation of lysosulfatide, 3',6'-anhydropsychosine, ceramide, and sphingosine by saponification of cerebroside sulfate. Effect of the sulfate group on the hydrolysis

Saponification of cerebroside sulfate (sulfatide) by refluxing with 1 N KOH in 90% n-butanol for 1 h yielded ceramide, sphingosine, lysosulfatide (psychosine-3'-sulfate ester) and a hitherto unknown compound. The latter compound was identified as 3,6-anhydrogalactosyl sphingosine (3',6'-anhydropsychosine) from its mass spectrum. The structure of lysosulfatide was confirmed by reacylating it to sulfatide by condensing it with lignoceroyl chloride. The resulting sulfatide, which was chromatographically identical to control sulfatides, was not oxidized by periodate. The sulfatide was also permethylated and methanolyzed. The sugar moiety obtained was identified as methyl 2,4,6-tri-O-methylgalactoside by gas-liquid chromatography and thin-layer chromatography. The presence of the sulfate group in lysosulfatide was further confirmed by IR spectroscopy and the presence of radioactivity when it was prepared from [35S]sulfatide. The effect of the sulfate group on cleavage of the galactoside linkage and on the formation of the 3,6-anhydro derivative is discussed.

New assay method for fatty acid synthetase with mass fragmentography

A new assay method for fatty acid synthetase using mass fragmentography is described. The amounts of fatty acids synthesized in deuterated water are determined by mass fragmentography by monitoring the intensities of m/e 77 and m/e 74 fragment ions using heptadecanoic acid as an internal standard. This method is suitable for any fatty acid synthetase which produces several species of fatty acids and is also applicable to crude enzyme preparations. This procedure is more sensitive and specific than the conventional spectrophotometric method. Fatty acid synthetases from rat liver and Brevibacterium ammoniagenes are analyzed by this method.

Antimicrobial activity of metal derivatives of sulfonamides

Antimicorbial activities of a series of metal derivatives of some sulfa drugs were examined. Such metal derivatives showed higher antimicorbial activity than the parent sulfa drugs, and among the metals, gold derivatives are seen to be the most effective.

Stereochemical studies of hydrogen incorporation from nucleotides with fatty acid synthetase from Brevibacterium ammoniagenes

The biosynthesis of fatty acids from malonyl-CoA and acetyl-CoA was investigated with an enzyme preparation which was purified 100-fold from Brevibacterium ammoniagenes. Fatty acids synthesized in the presence of D2O and stereospecifically deuterated NADPH and NADH were isolated and analyzed by mass chromatography to examine the localization of deuterium in the molecule. The following results were obtained: 1) HB hydrogen of NADPH was used for beta-ketoacyl reductase. 2) HB hydrogen of NADH was used for enoyl reductase. 3) Hydrogen atoms from water were found on the even-numbered methylene carbon atoms (2-hydrogen atoms per carbon atom) and some were also found on the odd-numbered methylene carbon. 4) Hydrogen atoms from NADPH were found on odd-numbered methylene carbon atoms (1-hydrogen per carbon). 5) Hydrogen atoms from NADH were also found on the odd-numbered methylene carbon atoms, but the number of incorporated hydrogen atoms was less than expected. The exchange of HB hydrogen of NADH with water catalyzed by enoyl reductase was suspected. 6) The exchange of methylene hydrogen atoms of malonyl-CoA with proton of water was suggested by 13C NMR analysis.

Origin of hydrogen atoms in the fatty acids synthesized with yeast fatty acid synthetase

The mechanism of hydrogen incorporation into fatty acids was investigated with an enzyme preparation from baker's yeast. Fatty acids synthesized from malonyl-CoA and acetyl-CoA in the presence of D2O or stereospecifically deuterium-labeled NADPH were isolated and analyzed by mass chromatography to examine the localization of deuterium atoms in the molecule. The following results were obtained: 1. Hydrogen atoms from water were found on the even-numbered methylene carbon atoms (2-hydrogen atoms per carbon atom). The second hydrogen atom was incorporated as the result of hydrogen exchange phenomenon between the methylene group of malonyl CoA and water. 2. HB hydrogen of NADPH was used for beta-ketoacyl reductase. 3. HB hydrogen of NADPH was also used for enoyl reductase. 4. Hydrogen atoms from HB position of NADPH were found on the odd-numbered methylene carbon atoms (2-hydrogen atoms per carbon atom).

Stereochemical studies of hydrogen incorporation from nucleotides with fatty acid synthetase from Brevibacterium ammoniagenes

The biosynthesis of fatty acids from malonyl-CoA and acetyl-CoA was investigated with an enzyme preparation which was purified 100-fold from Brevibacterium ammoniagenes. Fatty acids synthesized in the presence of D2O and stereospecifically deuterated NADPH and NADH were isolated and analyzed by mass chromatography to examine the localization of deuterium in the molecule. The following results were obtained: 1) HB hydrogen of NADPH was used for beta-ketoacyl reductase. 2) HB hydrogen of NADH was used for enoyl reductase. 3) Hydrogen atoms from water were found on the even-numbered methylene carbon atoms (2-hydrogen atoms per carbon atom) and some were also found on the odd-numbered methylene carbon atoms. 4) Hydrogen atoms from NADPH was found on the odd-numbered methylene carbon atoms (1 hydrogen per carbon). 5) Hydrogen atoms from NADH was also found on the odd-numbered methylene carbon atoms, but the number of incorporated hydrogen atoms was less than expected. The exchange of HB hydrogen of NADH with water catalyzed by enoyl reductase was suspected. 6) The exchange of methylene hydrogen atoms of malonyl-CoA with protons of water was suggested by 13C NMR analysis.

Quantitative determination of cholestanol in plasma with mass fragmentography. Biochemical diagnosis of cerebrotendinous xanthomatosis

A simple, sensitive, and accurate method for determination of cholestanol in plasma is described. In this method a fixed amount of cholestane is added to 1 ml of plasma as an internal standard and steroids are saponified and extracted with n-hexane. The amounts of cholestanol and cholesterol are determined by mass fragmentography by monitoring the intensities of m/e 306, m/e 329, and m/e 372 fragment ions. The relative standard deviation of results for cholestanol was about 6.3%. The cholestanol concentrations in the plasma, erythrocyte stroma, and plasma lipoproteins of three patients with cerebrotendinous xanthomatosis were determined by this method.