Wojciech Ambroziak

Metabolism of retinaldehyde and other aldehydes in soluble extracts of human liver and kidney.

Purification and characterization of enzymes metabolizing retinaldehyde, propionaldehyde, and octanaldehyde from four human livers and three kidneys were done to identify enzymes metabolizing retinaldehyde and their relationship to enzymes metabolizing other aldehydes. The tissue fractionation patterns from human liver and kidney were the same, indicating presence of the same enzymes in human liver and kidney. Moreover, in both organs the major NAD+-dependent retinaldehyde activity copurified with the propionaldehyde and octanaldehyde activities; in both organs the major NAD+-dependent retinaldehyde activity was associated with the E1 isozyme (coded for byaldh1 gene) of human aldehyde dehydrogenase. A small amount of NAD+-dependent retinaldehyde activity was associated with the E2 isozyme (product of aldh2 gene) of aldehyde dehydrogenase. Some NAD+-independent retinaldehyde activity in both organs was associated with aldehyde oxidase, which could be easily separated from dehydrogenases. Employing cellular retinoid-binding protein (CRBP), purified from human liver, demonstrated that E1 isozyme (but not E2 isozyme) could utilize CRBP-bound retinaldehyde as substrate, a feature thought to be specific to retinaldehyde dehydrogenases. This is the first report of CRBP-bound retinaldehyde functioning as substrate for aldehyde dehydrogenase of broad substrate specificity. Thus, it is concluded that in the human organism, retinaldehyde dehydrogenase (coded for by raldH1gene) and broad substrate specificity E1 (a member of EC 1.2.1.3aldehyde dehydrogenase family) are the same enzyme. These results suggest that the E1 isozyme may be more important to alcoholism than the acetaldehyde-metabolizing enzyme, E2, because competition between acetaldehyde and retinaldehyde could result in abnormalities associated with vitamin A metabolism and alcoholism.

Changes in the chemical form of selenium observed during the manufacture of a selenium-enriched sourdough bread for use in a human nutrition study

High-performance liquid chromatography interfaced with inductively coupled plasma mass spectrometry, and hydride generation-inductively coupled plasma mass spectrometry were used, respectively, to investigate changes in both the chemical form and the concentration of selenium during its bio-incorporation and bio-accumulation into rye seedlings. A 60-fold increase in the total level of selenium in the seedlings (‘control’ biomass = 0.99 mg kg−1, ‘enriched’ biomass = 55.27 mg kg−1) was accompanied by a change from selenite to several organo-selenium forms, with more than 40% being present as selenomethionine. The seedling biomass was dried, ground and used as an ingredient in the production of a fermented sourdough bread (popular in Poland and many Eastern European countries). The selenium in the resulting bread was also characterized in terms of its speciation, as well as its total selenium content (‘control’ bread = 0.06 mg kg−1, ‘enriched’ bread = 3.56 mg kg−1). The breads were then fed to 24 volunteers as part of a human intervention study designed to establish the efficacy of this mode of selenium supplementation. The human study data subsequently showed the bread was a good source of dietary selenium.

METABOLIC ROLE OF ALDEHYDE DEHYDROGENASE

Aldehyde dehydrogenase (EC 1.2.1.3), an enzyme with a broad substrate specificity and low Km values for short chain aliphatic aldehydes utilizes NAD as coenzyme, is universally distributed in mammalian livers and also at lower concentrations in other organs. The enzyme is a homotetramer of MW of ca. 220,000 (see review by Pietruszko, 1989). Because of its broad substrate specificity, it is frequently considered to be an enzyme of detoxication which functions in the organisms in oxidation of toxic aldehydes ingested in foodstuffs (see review by Jakoby and Ziegler, 1990). Metabolism of ethanol derived acetaldehyde, which is known to be catalyzed by this enzyme (Parrilla et al., 1974) is an example of detoxication role of aldehyde dehydrogenase. In the human liver the enzyme occurs as three known isozymes, El, E2 and E3; other isozymes not yet identified may exist.

Effect of Microencapsulation by Spray-Drying and Freeze-Drying Technique on the Antioxidant Properties of Blueberry (Vaccinium myrtillus) Juice Polyphenolic Compounds

Abstract Blueberry juice with high polyphenol concentration was spray- or freeze-dried using different coating materials: HP-β-cyclodextrin and β-cyclodextrin. The quality of the obtained powders was characterised by their anthocyanin content, total polyphenols and antioxidant capacity. SEM was used for monitoring structures and size (2–20 μm) of the microparticles. The losses of total phenolic compounds during spray-drying reached 76–78% on average, while these of anthocyanins about 57%. Freeze-dried powders showed better retention values of anthocyanins, which was about 1.5-fold higher than for the spray-dried counterparts. All blueberry preparations studied were characterised by very high radical scavenging activity.

Enhancing adhesion of yeast brewery strains to chamotte carriers through aminosilane surface modification

The adhesion of cells to solid supports is described as surface-dependent, being largely determined by the properties of the surface. In this study, ceramic surfaces modified using different organosilanes were tested for proadhesive properties using industrial brewery yeast strains in different physiological states. Eight brewing strains were tested: bottom-fermenting Saccharomyces pastorianus and top-fermenting Saccharomyces cerevisiae. To determine adhesion efficiency light microscopy, scanning electron microscopy and the fluorymetric method were used. Modification of chamotte carriers by 3-(3-anino-2-hydroxy-1-propoxy) propyldimethoxysilane and 3-(N, N-dimethyl-N-2-hydroxyethyl) ammonium propyldimethoxysilane groups increased their biomass load significantly.

Aldehyde dehydrogenase (EC 1.2.1.3): Comparison of subcellular localization of the third isozyme that dehydrogenates γ-aminobutyraldehyde in rat, guinea pig and human liver

1. Subcellular fractionation of rat, guinea pig and human livers showed that aldehyde dehydrogenase metabolizing gamma-aminobutyraldehyde was exclusively localized in the cytoplasmic fraction in all three mammalian species. 2. Total gamma-aminobutyraldehyde activity of aldehyde dehydrogenase was found to be ca 0.41, 0.3 and 0.24 mumol NADH min-1 g-1 tissue, respectively in rat, guinea pig and human liver, with more than 95% of activity in the cytoplasm. 3. Partially purified cytoplasmic isozyme from rat liver showed similar chromatographic behavior and kinetic properties to the E3 isozyme isolated from human liver. 4. The rat isozyme was insensitive to disulfiram (40 microM) and to magnesium (160 microM) and had Km values of 5 microM (pH 7.4) for gamma-aminobutyraldehyde, 7.5 microM (pH 9.0) for propionaldehyde and 4 microM (pH 7.4) for NAD.

Physiological tests for yeast brewery cells immobilized on modified chamotte carrier

In this study yeast cell physiological activity was assessed on the basis of the in situ activity of two important enzymes, succinate dehydrogenase and pyruvate decarboxylase. FUN1 dye bioconversion and cellular ATP content were also taken as important indicators of yeast cell activity. The study was conducted on six brewing yeast strains, which were either free cells or immobilized on a chamotte carrier. The experimental data obtained indicate clearly that, in most cases, the immobilized cells showed lower enzyme activity than free cells from analogous cultures. Pyruvate decarboxylase activity in immobilized cells was higher than in planktonic cell populations only in the case of the Saccharomyces pastorianus 680 strain. However, in a comparative assessment of the fermentation process, conducted with the use of free and immobilized cells, much more favorable dynamics and carbon dioxide productivity were observed in immobilized cells, especially in the case of brewing lager yeast strains. This may explain the higher total cell density per volume unit of the fermented medium and the improved resistance of immobilized cells to environmental changes.

Decrease of wheat flour allergenicity via lactic acid fermentation

Abstract Results of the research on the lowering of allergenicity of wheat flour fermented using homo- and heterofermentative lactic acid bacteria and mixed cultures with yeast were discussed. The gliadins’ immunoreactivity was measured using the indirect non-competitive enzyme-linked immunosorbent assay method. The biggest decrease of the immunoreactivity of gliadin fraction was observed in the case of fermentation performed with the use of mixed cultures of lactic acid bacteria and yeast. This way of wheat flour modification seems to be promising, because fermentation is a natural process causing not only lowering of the allergenicity, but also improving organoleptic and nutritional values of obtained products.

Effect of cholesta-3,5-dien-7-one on human liver aldehyde dehydrogenase

A recently isolated cholesterol oxidation product, cholesta-3,5-dien-7-one, which was present at high concentrations in fatty/cirrhotic alcoholic liver was identified as a potent endogenous inhibitor of the cytosolic, E1, isozyme of aldehyde dehydrogenase (EC 1.2.1.3). The oxysterol was a less potent inhibitor of mitochondrial, E2, isozyme. The inhibition of the E1 isozyme was irreversible on the IEF gels, upon dilution and with 33 microM 2-mercaptoethanol during activity assay. The calculated 1-50% values from the inhibition curves for the E1 isozyme were 5-10 microM and approx. 180 microM for the E2 isozyme. The E3 isozyme was not sensitive to the oxysterol. Judging from the Lineweaver-Burk plot, the inhibition of the E1 isozyme with a constant concentration of cholesta-3,5-dien-7-one (52 microM) appeared to be noncompetitive.

Bacteria/yeast and plant biomass enriched in Se via bioconversion process as a source of Se supplementation in food

Mono and mixed populations of lactic acid bacteria of Lactobacillus species ( Lb. plantarum, Lb. sanfrancisco, Lb. brevis ) and the yeast Saccharomyces cerevisiae were tested for their ability to accumulate Se from the culture medium containing different inorganic Se sources (SeO 2 , Na 2 SeO 3 , Na 2 SeO 4 ). A high correlation between Se concentration in culture medium and Se content in biomass was observed. The highest amounts of Se in Lactobacillus species was observed with Lb. plantarum and the lowest one with Lb. sanfrancisco . Under the same conditions yeast accumulated considerable lower amounts of selenium. In all tested strains at concentrations higher than 10 μg Se/ml in the medium, there was an abrupt increase in Se content in the biomass with associated brick red color of free amorphous selenium deposit. At all Se levels a negative effect on growth parameters was observed. However, in a mixed population a stimulating effect on selenium accumulation and the growth parameters has been seen. For all strains selenite was the best and selenate the worst source of selenium. Plant seeds and grains were germinated during 3–5 days on culture plates rinsed with water containing different concentrations (1–30 μg Se/ml) of inorganic selenium. Screening tests have shown different Se accumulation for individual plants. Similar accumulations of Se with tap, mineral and distilled water and with Se inorganic source of +4 or +6 oxidation state were seen. A one-stage fermentation process of bread production was used to test an effect of Se-enriched plant and bacteria-yeast biomass on the fermentation process. Technological parameters and bread quality of regular and Se-enriched bread (with 70–80 μg Se/250g) were comparable.