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Results for “Galactosephosphates”

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17 recordsLinked to original sources
PubMed1978

Association of presenile cataracts with heterozygosity for galactosaemic states and with riboflavin deficiency.

Red cells and the lens of the eye are non-nucleated cells; moreover, they have metabolic similarities. Cataracts develop in childhood in homozygotes for galactosaemic abnormalities, which can be detected by biochemical measurements in red blood-cells. It has not been determined whether heterozygotes for these defects are at greater risk for cataract development later in life. Similarly, riboflavin deficiecy for which the erythrocyte is a sensitive indicator, has been associated with cataracts in animals. Red-cell studies were carried out in 22 patients, aged under 50, with cataracts. Heterozygosity for galactokinase deficiency was detected in 5 patients, for galactose-uridyl transferase in 2, and evidence of an erythrocytic deficiency of riboflavin in 8. Even when Black subjects were excluded from analysis because of their high incidence of polymorphism for galactokinase, these findings are significantly different from those expected from population surveys and suggest that many patients with presenile cataracts have a biochemical abnormality which can be detected by examination of red blood-cells and which may be corrected by dietary restrictions or supplements.

Adolescent↗
PubMed1978

Galactose-1-phosphate accumulation by a Duarte-transferase deficiency double heterozygote.

An infant, suspected of having galactosemia following a positive screening test on dried blood spots, was shown to be a Duarte-transferase deficiency compound heterozygote through studies of electrophoretic mobility of the transferase enzyme in blood from the patient and family members. No rise in blood glucose was seen following oral ingestion of galactose. At the same time, galactose rose in plasma and was excreted in the urine; galactose-1-phosphate accumulated in erythrocytes. A galactose-free diet was considered the prudent course in the presence of the patient's inability to metabolize galactose completely.

Blood Glucose↗
PubMed1979

Galactosemia: alterations in sulfate metabolism secondary to galactose-1-phosphate uridyltransferase deficiency.

Cultures of nonmutant as well as galactokinase-deficient fibroblasts incorporate 20 percent more [35S]sulfate when galactose is substituted for glucose in the medium; galactose-1-phosphate uridyltransferase-deficient cells incorporate 65.5 percent less. In addition to incorporating less [35S]sulfate, the uridyltransferase-deficient cells showed significant accumulation of intracellular galactose-1-phosphate within 4 hours after galactose exposure. Under the same conditions, no difference in [3H]uridine incorporation was observed. This metabolic alteration, occurring in response to galactose exposure, may be related to the pathophysiology of classical galactosemia.

Cells, Cultured↗
PubMed1979

Regulation of lactose catabolism in Streptococcus mutans: purification and regulatory properties of phospho-beta-galactosidase.

Phospho-beta-galactosidase (P-beta-gal), the enzyme which catalyzes the first step in the metabolism of intracellular lactose phosphate, occurred at high specific activity in the cytoplasm in 12 of 13 strains of streptococcus mutans grown on lactose but not other carbon sources. The P-beta-gal from S. mutans SL1 was purified 13-fold using diethylaminoethyl-cellulose ion exchange and agarose A--0.5 M molecular exclusion column chromatography. The molecualr weight of the enzyme was estimated to be 40,000, and its pH optimum was 6.5 in three different buffer systems. P-beta-gal activity was inhibited by Co2+, Zn2+, and Cu2+, but other cations, ethylenediaminetetraacetic acid, orthophosphate, and fluoride had no effect upon enzyme activity. The kinetic response of P-beta-gal to a model substrate, o-nitrophenyl-beta-D-galactopyranoside-6-phosphate, obeyed Michaelis-Menten kinetics, and the Km for this substrate was 0.19 mM. In addition to being under genetic control, P-beta-gal activity was regulated by a number of biologically active metabolites. Enzyme activity was inhibited in a sigmoidal fashion by phosphoenolpyruvate. The M 0.5 V value for phosphoenolpyruvate was 2.8 mM, and the Hill coefficient (n) was 3. In addition, P-beta-gal exhibited strong inhibition by ATP, galactose-6-phosphate, and glucose-6-phosphate. In contrast to inhibition of P-beta-gal activity by phosphoenolpyruvate, the inhibition exerted by ATP, galactose-6-phosphate, and glucose-6-phosphate obeyed classical Michaelis-Menten kinetics; the Ki values for these inhibitors were 0.55, 1.6, and 4.0 mM, respectively.

Adenosine Triphosphate↗
PubMed1979

Lactose metabolism involving phospho-beta-galactosidase in Klebsiella.

Klebsiella strain RE1755A is a Lac- Gal- mutant which has lost both of its lac operons, but possesses a gene specifying beta-galactosidase III, an enzyme which hydrolyzes o-nitrophenyl-beta-D-galactopyranoside but does not hydrolyze lactose. Selective pressure was applied to isolate mutants able to utilize lactose. The lactose-utilizing mutants obtained were shown to possess an unaltered beta-galactosidase III. Lactose utilization was shown to result from a pleiotropic mutation which also (i) permits galactose utilization and (ii) prevents induction of beta-galactosidase III synthesis by lactose. Evidence is presented suggesting that a phospho-beta-galactosidase enzyme is involved in lactose metabolism.

Galactosephosphates↗
PubMed1979

Lactose metabolism in Streptococcus lactis: phosphorylation of galactose and glucose moieties in vivo.

Starved cells of Streptococcus lactis ML3 grown previously on lactose, galactose, or maltose were devoid of adenosine 5'-triphosphate contained only three glycolytic intermediates: 3-phosphoglycerate, 2-phosphoglycerate, and phosphoenolpyruvate (PEP). The three metabolites (total concentration, ca 40 mM) served as the intracellular PEP potential for sugar transport via PEP-dependent phosphotransferase systems. When accumulation of [14C]lactose by iodoacetate-inhibited starved cells was abolished within 1 s of commencement of transport, a phosphorylated disaccharide was identified by autoradiography. The compound was isolated by ion-exchange (borate) chromatography, and enzymatic analysis showed that the derivative was 6-phosphoryl-O-beta-D-galactopyranosyl (1 leads to 4')-alpha-D-glucopyranose (lactose 6-phosphate). After maximum lactose uptake (ca. 15 mM in 15 s) the cells were collected by membrane filtration and extracted with trichloroacetic acid. Neither free nor phosphorylated lactose was detected in cell extracts, but enzymatic analysis revealed high levels of galactose 6-phosphate and glucose 6-phosphate. The starved organisms rapidly accumulated glucose, 2-deoxy-D-glucose, methyl-beta-D-thiogalactopyranoside, and o-nitrophenyl-beta-D-galactopyranoside in phosphorylated form to intracellular concentrations of 32, 32, 42, and 38.5 mM, respectively. In contrast, maximum accumulation of lactose (ca. 15 mM) was only 40 to 50% that of the monosaccharides. From the stoichiometry of PEP-dependent lactose transport and the results of enzymatic analysis, it was concluded that (i) ca. 60% of the PEP potential was utilized via the lactose phosphotransferase system for phosphorylation of the galactosyl moiety of the disaccharide, and (ii) the residual potential (ca. 40%) was consumed during phosphorylation of the glucose moiety.

Biological Transport, Active↗
PubMed1978

beta-D-phosphogalactoside galactohydrolase of Streptococcus faecalis and the inhibition of its synthesis by glucose.

The lactose hydrolysing system of Streptococcus faecalis is described. It is closely related to that one of the group N streptocci as it consists of a beta-D-phosphogalactoside galactohydrolase (beta-Pgal). The uptake of methyl-beta-D-thiogalactoside (TMG), lactose, and glucose is maintained by the phosphoenolpyruvate-dependent phosphotransferase system (PTS) but the uptake of galactose is not. The induction time is 6--7 min. Inducers are lactose and galactose but not isopropyl-beta-D-galactoside (IPTG) and TMG. In the presence of glucose, mannose, and maltose no induction of beta-Pgal occurs but pyruvate and glycerol allow induction. The competitive inhibition of uptake of TMG by glucose suggests inducer exclusion by this sugar. TMG accumulates in the cells exclusively as a derivative.

Enterococcus faecalis↗
PubMed1977

Kinetics of ethanol inhibition of galactose elimination in perfused pig liver.

The effect of ethanol (5--25 mM) on the galactose elimination kinetics in the intact liver was studied in the isolated perfused pig liver, using the steady-state infusion technique. Ethanol reduced galactose-Vmax on average to 0.07 mmol/min kg liver in six experiments from 0.43 mmol/min kg obtained in control experiments without ethanol. Also Km was significantly reduced from 0.23 mmol/l plasma water to 0.03 mmol/l. Ethanol increased UDP-galactose ten-fold simultaneous with a rise in hepatic outflow ratio of lactate to pyruvate to about 300 from 10; this indicates that ethanol inhibits epimerase. In experiments with increasing galactose elimination rates, the concentration of galactose-1-P increased much less than the concentration of galactose, and the phosphorylation of galactose therefore seems to be rate-limiting. In vitro galactokinase is inhibited by galactose-1-P. In the present study ethanol increased galactose-1-P five to ten times, and the reduction of Vmax and Km by ethanol could be explained by uncompetitive inhibition by galactose-1-P with Ki about 0.1 mmol/l. Ethanol decreased UDP-glucose to about 40% and UTP to less than 5%, probably due to trapping as UDP-galactose. This may depress the forward transferase reaction, and therefore the other co-substrate galactose-1-P rises--and inhibits galactokinase.

Adenosine Diphosphate↗
PubMed1979

Galactose-1-phosphate uridylyltransferase activity in chronic lymphocytic leukemia.

Galactose-1-phosphate uridylytransferase (E.C.2.7.12) activity was measured in both lymphoid and erythroid cells from patients with chronic lymphocytic leukemia (CLL). Decreased enzyme activity was found in both cell types using two assay methods. The results suggest the presence of an inhibitor of the enzyme in CLL patients. A correlation between decreased uridyl transferase activity and glycogen accumulation in CLL is postulated.

Erythrocytes↗
PubMed1977

[Glucose-6-phosphate dehydrogenase deficiency of erythrocytes in the GDR].

34 persons with G-6-PD deficiency were diagnosed, and the pathological enzyme-variants of red blood cells were characterized according to the recommendations of WHO. We conclude from the differing residual G-6-PD-activities in red blood cells of the propositi and the differing reactivity of the enzyme in kinetic and physicochemical characterizations that a multiple variety of rare pathological G-6-PD variants exists in the GDR. Using the estimated enzymeparameters it was not possible in all cases to compare directly the newly demonstrated G-6-PD variants with cases already described in the literature. In addition, the differing combinations of parameters render a classification more difficult.

Electrophoresis↗
PubMed1979

[Clinical and biochemical diagnosis of galactosemia among our cases].

Clinical and biochemical diagnostic studies concerned 17 cases of galactosemia coming from 15 not consauguineous families. Galactosemia was diagnosed between 1-st day and 11-th month of life. Tentative diagnosis based on clinical picture was made in 12 infants, others were detected through family history of galactosemia and/or biochemical newborn screening carried out at the National Research Institute of Mother and Child since 1969. Clinical symptoms of galactosemia occurred in most patients in the first week of life. They were the following (tab. II): hepatomegaly (in 94%), jaundice (81%), splenomegaly (79%), vomitus (62%) and diarrhoea in 56% of patients. Cataract was found in 6 infants (38%). Biochemical diagnosis was based on the results of enzymatic estimation of galactose-1-phosphate uridyl transferase activity in blood, galactose-1-phosphate in red blood cells and galactose in blood and urine. No activity of galactose-1-phosphate uridyl transferase was found in all patients, and the concentration of galactose-1-phosphate was higher than 25 mg/100 ml of red blood cells. High galactose level was observed in blood and urine in all patients with typical clinical course of galactosemia. In 2 patients however without clinical symptoms of the disease only trace amounts of galactose was detected in blood and urine. All these patients were treated with galactose free diet.

Adult↗
PubMedDate not supplied

Disorders of galactose metabolism.

Galactose metabolism occupies a central position in modern biology through its relationship to cell surface antigenicity and its metabolic function as a component of glycolipids and glycoproteins. Disturbances in three fundamental reaction sequences of this hexose have led to a delineation of pathways of the chemistry resulting in the understanding of its metabolic fate. These inherited disorders of metabolism are prototypes for the application of nutritional therapy of biochemical genetic defects.

Animals↗