Interaction of aldehydes with glyoxalase I and the status of several aldehyde metabolizing enzymes of Ehrlich ascites carcinoma cells.

Abstract: Aldehydes are organic compounds that are widespread in nature. They can be formed endogenously by lipid peroxidation (LPO), carbohydrate or metabolism ascorbate autoxidation, amine oxidases, cytochrome P-450s, or myeloperoxidase-catalyzed metabolic activation. This review compares the reactivity of many aldehydes towards biomolecules particularly macromolecules. Furthermore, it includes not only aldehydes of environmental or occupational concerns but also dietary aldehydes and aldehydes formed endogenously by intermediary metabolism. Drugs that are aldehydes or form reactive aldehyde metabolites that cause side-effect toxicity are also included. The effects of these aldehydes on biological function, their contribution to human diseases, and the role of nucleic acid and protein carbonylation/oxidation in mutagenicity and cytotoxicity mechanisms, respectively, as well as carbonyl signal transduction and gene expression, are reviewed. Aldehyde metabolic activation and detoxication by metabolizing enzymes are also reviewed, as well as the toxicological and anticancer therapeutic effects of metabolizing enzyme inhibitors. The human health risks from clinical and animal research studies are reviewed, including aldehydes as haptens in allergenic hypersensitivity diseases, respiratory allergies, and idiosyncratic drug toxicity; the potential carcinogenic risks of the carbonyl body burden; and the toxic effects of aldehydes in liver disease, embryo toxicity/teratogenicity, diabetes/hypertension, sclerosing peritonitis, cerebral ischemia/neurodegenerative diseases, and other aging-associated diseases.

Abstract: Publisher Summary The turbidity produced when protein is mixed with low concentrations of any of the common protein precipitants can be used as an index of protein concentration. The resulting turbidity is maximum after about 10 minutes and may be measured spectrophotometrically in the wavelength region of 600 m. Standardization may be effected by comparison with the turbidity produced by a suspension of a dried protein precipitate, or reference may be had to the methyl acrylate-styrene polymer. Turbidimetric techniques are rapid and convenient, but they yield different values with different proteins. They do not permit differentiation between protein and acid-insoluble compounds such as nucleic acids. Protein estimation with the Folin-Ciocalteu reagent include (1) biuret reaction of protein with copper ion in alkali, and (2) reduction of the phosphomolybdic-phosphotungstic reagent by the tyrosine and tryptophan present in the treated protein. Protein estimation by ultraviolet absorption takes advantage of the fact that nucleic acid, however, absorbs much more strongly at 260 mμ than at 280 mμ, whereas with protein the reverse is true. This advantage is used to eliminate, by calculation, the interference of nucleic acids in the estimation of protein.

Abstract: The glyoxalase system is present in the cytosol of cells and cellular organelles, particularly mitochondria. It is found throughout biological life and is thought to be ubiquitous. The widespread distribution and presence of the glyoxalase system in living organisms suggests it fulfils a function of fundamental importance to biological life. Recent investigations have brought new developments in the involvement of the glyoxalase in cell growth and vesicle mobilization, with increasing evidence of changes in the glyoxalase system during tumor growth and diabete mellitus, particularly relating to the development of associated clinical complications.

Abstract: The central glycolytic and oxidative pathways and the ATP-producing mechanisms differ in sane and malignant cells by their regulation and dynamics. Fast-growing, poorly-differentiated cancer cells characteristically show high aerobic glycolysis. In the same way, cholesterol biosynthesis, which occurs by normal pathways in tumors, is deficient in feed-back regulation and in sterol-transport mechanisms. Other metabolic ways are deficient, as for example, intramitochondrial aldehyde catabolism, at the origin of a possible acetaldehyde toxicity, which can be circumvented by the synthesis of an unusual and neutral product for mammalian cells acetoin, through tumoral pyruvate dehydrogenase. If most of the glycolytic pyruvate is deviated to lactate production, little of the remaining carbons enter a truncated Krebs cycle where citrate is preferentially extruded to the cytosol where it feeds sterol synthesis. Glutamine is the major oxidizable substrate by tumor cells. Inside the mitochondrion, it is deaminated to glutamate through a phosphate-dependent glutaminase. Glutamate is then preferentially transaminated to alpha-ketoglutarate that enters the Krebs cycle. Glutamine may be completely oxidized through the abnormal Krebs cycle only if a way of forming acetyl CoA is present: cytosolic malate entering mitochondria is preferentially oxidized to pyruvate + CO2 through an intramitochondrial NAD(P)(+)-malic enzyme, whereas intramitochondrial malate is preferentially oxidized to oxaloacetate through malate dehydrogenase, thus providing a high level of intramitochondrial substrate compartmentation. These and other regulatory aberrations in tumor cells appear to be reflections of a complex set of non-random phenotypic changes, initiated by expression of oncogenes.