Galactose Metabolites Research Articles

Development of a protocol for newborn screening for disorders of the galactose metabolic pathway.

The protocol evaluated in this paper employs an enzymatic assay of galactose metabolites, thin layer chromatography, and an assay of galactose-1-phosphate uridyl transferase on a single sample of blood collected routinely for newborn screening. Its effectiveness was tested by a retrospective study of known galactosemic blood samples, and also by a prospective study of 207,000 newborn samples from which 6 infants with severe transferase deficient galactosaemia and 2 infants with red cell epimerase deficiency were identified. The detection rate for severe transferase deficiency in the newborn population was 1:35,000. Advantages include low false positive rate, definitive diagnosis within 6 hours of sample receipt, and the use of technically simple and robust procedures. This protocol overcomes the difficulties encountered with previously described procedures.

The galactose elimination capacity as a quantitative measure of liver function in acute carbon tetrachloride intoxication of rats.

In rats given rising single doses of carbon tetrachloride (CCl4) intragastrically the relation between dose and mortality, between time after injection and the quantitative liver function measured by the galactose elimination capacity (GEC), and between the dose and the GEC, was examined. The change in hepatic contents of galactose metabolites after CCl4 was measured. There was a linear relation between the dose and mortality. No rat died later than 36 h after injection. Following injection of a dose lethal to 15% of rats the GEC fell to 40% of control after 36 h and was normalized after 72 h. There was a dose dependent decrease in the GEC with rising doses given 36 h earlier up to a dose lethal to 15%. Galactose metabolites other than UDP-galactose, which was decreased, were not affected by CCl4, suggesting a general enzyme depression. The results are compatible with the concept of proportionality between the GEC and 'the functioning liver mass' and indicate that the GEC presents prognostically valuable information during acute hepatic insufficiency.

Studies on galactose metabolism in heart and brain: The identification of d-galactose 6-phosphate in brains of galactose-intoxicated chicks and rat hearts perfused with galactose

Leloir pathway enzyme activities of adult rat heart were present in amounts 8, 38, and 23% that of adult rat liver for galactokinase, galactose 1-phosphate uridyl transferase, and UDP-galactose 4′-epimerase, respectively. The corresponding values for the adult rat brain enzymes relative to liver were 27, 11, and 120%, respectively. Michaelis constants for the three enzymes were comparable in heart, brain, and liver of the adult rat. While diminished galactokinase activity correlated well with the established limited ability of brain and heart to metabolize galactose, the low uridyl transferase activity of adult rat brain could also contribute to its restricted galactose utilization. Rat heart and brain, but not liver, soluble enzyme preparations produced in addition to galactose 1-phosphate, a metabolite tentatively identified as galactose 6-phosphate when incubated with high concentrations of d-galactose (30 m m). Galactose 6-phosphate was further identified in the brains of galactose-intoxicated chicks and rat hearts perfused with d-galactose by spectrophotometry and analysis by combined gas-liquid chromatography-mass spectrometry. Tissue concentrations of galactose 6-phosphate were compared to selected glycolytic and galactose metabolites.

Galactose elimination capacity in the rat.

The elimination of galactose infused in rats was found to follow saturation kinetics with estimated maximal elimination rate 122 μmol per h and 200 g body weight and estimated half saturation concentration 0.4 mmol/1. The galactose elimination capacity (GEC) is defined as the elimination rates determined at blood concentrations between 6 and 20 time Km. Multiple regression analysis demonstrates that both body weight and liver weight are determining for GEC. The relation between elimination rate and concentration of galactose metabolites in liver tissue indicates that the phosphorylation of galactose is rate limiting in the metabolism of galactose.

Resistance of Salmonella typhimurium mutants to galactose death.

A class of galactose-resistant mutants has been derived from strains of Salmonella typhimurium which are defective in uridine diphosphoglucose-4-epimerase. Resistant strains are phenotypically similar to parent organisms but do not lyse in the presence of galactose. Low levels of functional epimerase can be detected in induced cells grown at 20 C but not at 37 C, and acid is not produced from galactose. Sufficient galactose is synthesized at reduced temperatures to fabricate smooth lipopolysaccharide and acceptor sites for phage P22 from galactose-deficient media. The leaky nature of these mutants may account for resistance to galactose death by maintaining galactose metabolites at a subcritical level. Glucose protects sensitive strains by control of levels of toxic metabolites by catabolite repression.