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Stanton Segal – One of the best experts on this subject based on the ideXlab platform.

  • The rate of de novo Galactose synthesis in patients with Galactose-1-phosphate uridyltransferase deficiency
    Molecular Genetics and Metabolism, 2020
    Co-Authors: Gerard T. Berry, Cong Ning, Robert Reynolds, Claire Yager, Peter J. Moate, Raymond C. Boston, Stanton Segal
    Abstract:

    Abstract Using both a continuous infuinfusion of isotopically labeled [1-13C]Galactose with a steady-state analysis and a single injection kinetic approach, we have calculated the apparent Galactose appearance rate (GAR) in patients with Galactose-1-phosphate uridyltransferase deficiency and control subjects. With the steady-state protocol, the GAR in 18 patients less than 18 years of age was 1.34 ± 0.53 mg/kg/h (mean ± SD) and was significantly greater than the mean of 0.56 ± 0.01 mg/kg/h (p=0.004) in five patients above 18 years of age. Patients who were given a priming dose of [1-13C]Galactose had a reduced GAR compared to those without a priming dose, 0.73 ± 0.05 (n=9) vs 1.46 ± 0.62 (n=14) mg/kg/h (p=0.005). The GAR in controls was lower than in patients ranging from 0.58 to 0.68 mg/kg/h in children and 0.07–0.09 mg/kg/h in adults. In the single bolus studies the plasma [13C]Galactose enrichment decreased in a biexponential pattern suggesting at least a two-compartment system. The calculated GAR in three adult patients was similar to that found in them by the continuous infuinfusion technique. The GAR in patients suggests the source of Galactose for the continued elevation of Galactose metabolites as well as the basis for the long-term complications in Galactosemia despite restricted dietary Galactose intake.

  • Evidence for function of UDP Galactose pyrophosphorylase in mice with absent Galactose-1-phosphate uridyltransferase
    Molecular Genetics and Metabolism, 2007
    Co-Authors: Suzanne L. Wehrli, Robert Reynolds, Stanton Segal
    Abstract:

    Abstract Mice with deletion of the Galactose-1-phosphate uridyltransferase (GALT) gene were examined for their ability to form 13 C labeled hepatic UDP glucose from administered 1- 13 C Galactose. NMR analysis of urinary acetaminophen glucuronide, which is derived from hepatic UDP glucose showed 13 C enrichment after concomitant administration of 13 C Galactose and acetaminophen. The finding is consistent with the function of UDP Galactose pyrophosphorylase as an alternate pathway of Galactose metabolism.

  • UDP-Galactose pyrophosphorylase in mice with Galactose-1-phosphate uridyltransferase deficiency.
    Molecular Genetics and Metabolism, 2005
    Co-Authors: Nancy D. Leslie, Claire Yager, Robert Reynolds, Stanton Segal
    Abstract:

    Abstract UDP-glucose pyrophosphorylase (E.C. 2.7.7.9), encoded by ugp , provides UDP-glucose which is critical to the synthesis of glycogen, and also catalyzes the reaction between UTP and Galactose-1-phosphate, yielding UDP-Galactose. This activity of UDP-gal pyrophosphorylase (UDP-galPP) suggests a role in an alternate pathway for Galactose metabolism in patients with deficiency of Galactose-1-phosphate uridyltransferase (GALT). We examined the effects of GALT deficiency and dietary Galactose on UDP-glucose pyrophosphorylase (UDP-gluPP) and UDP-Galactose pyrophosphorylase activity and ugp expression in liver of mice with homozygous deletion of the critical regions of galt. Activity with glucose-1-phosphate as substrate was significantly higher than that with Galactose-1-phosphate. In liver from mice with GALT deficiency (G/G), UDP-galPP activity appeared to be lower than that measured in liver from control (N/N) animals. This difference disappeared when the N/N tissue homogenate was dialyzed to remove residual UDP-glucose, confirming that careful elimination of residual GALT activity is necessary, since GALT has 1000-fold greater activity toward Galactose-1-phosphate than that of UDP-galPP in liver homogenates. Prior exposure to conventional mouse chow, high Galactose chow, and high glucose chow did not alter UDP-glu PP or UDP-galPP activity. Steady state UGP mRNA levels were determined in tissues from normal and G/G animals. UGP expression was highest in liver, and did not differ by genotype or exposure to high Galactose chow. UDP-galPP activity may account for unexplained ability to oxidize Galactose in animals with no GALT activity, but is insufficient to alter accumulation of Galactose metabolites.

Perry A Frey – One of the best experts on this subject based on the ideXlab platform.

Robert Reynolds – One of the best experts on this subject based on the ideXlab platform.

  • The rate of de novo Galactose synthesis in patients with Galactose-1-phosphate uridyltransferase deficiency
    Molecular Genetics and Metabolism, 2020
    Co-Authors: Gerard T. Berry, Cong Ning, Robert Reynolds, Claire Yager, Peter J. Moate, Raymond C. Boston, Stanton Segal
    Abstract:

    Abstract Using both a continuous infusion of isotopically labeled [1-13C]Galactose with a steady-state analysis and a single injection kinetic approach, we have calculated the apparent Galactose appearance rate (GAR) in patients with Galactose-1-phosphate uridyltransferase deficiency and control subjects. With the steady-state protocol, the GAR in 18 patients less than 18 years of age was 1.34 ± 0.53 mg/kg/h (mean ± SD) and was significantly greater than the mean of 0.56 ± 0.01 mg/kg/h (p=0.004) in five patients above 18 years of age. Patients who were given a priming dose of [1-13C]Galactose had a reduced GAR compared to those without a priming dose, 0.73 ± 0.05 (n=9) vs 1.46 ± 0.62 (n=14) mg/kg/h (p=0.005). The GAR in controls was lower than in patients ranging from 0.58 to 0.68 mg/kg/h in children and 0.07–0.09 mg/kg/h in adults. In the single bolus studies the plasma [13C]Galactose enrichment decreased in a biexponential pattern suggesting at least a two-compartment system. The calculated GAR in three adult patients was similar to that found in them by the continuous infusion technique. The GAR in patients suggests the source of Galactose for the continued elevation of Galactose metabolites as well as the basis for the long-term complications in Galactosemia despite restricted dietary Galactose intake.

  • Evidence for function of UDP Galactose pyrophosphorylase in mice with absent Galactose-1-phosphate uridyltransferase
    Molecular Genetics and Metabolism, 2007
    Co-Authors: Suzanne L. Wehrli, Robert Reynolds, Stanton Segal
    Abstract:

    Abstract Mice with deletion of the Galactose-1-phosphate uridyltransferase (GALT) gene were examined for their ability to form 13 C labeled hepatic UDP glucose from administered 1- 13 C Galactose. NMR analysis of urinary acetaminophen glucuronide, which is derived from hepatic UDP glucose showed 13 C enrichment after concomitant administration of 13 C Galactose and acetaminophen. The finding is consistent with the function of UDP Galactose pyrophosphorylase as an alternate pathway of Galactose metabolism.

  • UDP-Galactose pyrophosphorylase in mice with Galactose-1-phosphate uridyltransferase deficiency.
    Molecular Genetics and Metabolism, 2005
    Co-Authors: Nancy D. Leslie, Claire Yager, Robert Reynolds, Stanton Segal
    Abstract:

    Abstract UDP-glucose pyrophosphorylase (E.C. 2.7.7.9), encoded by ugp , provides UDP-glucose which is critical to the synthesis of glycogen, and also catalyzes the reaction between UTP and Galactose-1-phosphate, yielding UDP-Galactose. This activity of UDP-gal pyrophosphorylase (UDP-galPP) suggests a role in an alternate pathway for Galactose metabolism in patients with deficiency of Galactose-1-phosphate uridyltransferase (GALT). We examined the effects of GALT deficiency and dietary Galactose on UDP-glucose pyrophosphorylase (UDP-gluPP) and UDP-Galactose pyrophosphorylase activity and ugp expression in liver of mice with homozygous deletion of the critical regions of galt. Activity with glucose-1-phosphate as substrate was significantly higher than that with Galactose-1-phosphate. In liver from mice with GALT deficiency (G/G), UDP-galPP activity appeared to be lower than that measured in liver from control (N/N) animals. This difference disappeared when the N/N tissue homogenate was dialyzed to remove residual UDP-glucose, confirming that careful elimination of residual GALT activity is necessary, since GALT has 1000-fold greater activity toward Galactose-1-phosphate than that of UDP-galPP in liver homogenates. Prior exposure to conventional mouse chow, high Galactose chow, and high glucose chow did not alter UDP-glu PP or UDP-galPP activity. Steady state UGP mRNA levels were determined in tissues from normal and G/G animals. UGP expression was highest in liver, and did not differ by genotype or exposure to high Galactose chow. UDP-galPP activity may account for unexplained ability to oxidize Galactose in animals with no GALT activity, but is insufficient to alter accumulation of Galactose metabolites.

J P Latge – One of the best experts on this subject based on the ideXlab platform.

  • overlapping and distinct roles of aspergillus fumigatus udp glucose 4 epimerases in Galactose metabolism and the synthesis of Galactose containing cell wall polysaccharides
    Journal of Biological Chemistry, 2014
    Co-Authors: Fabrice N Gravelat, Robert P Cerone, Stefanie D Baptista, Paolo Campoli, Sein Choe, Ilia Kravtsov, Evgeny Vinogradov, Carole Creuzenet, Albert M Berghuis, J P Latge
    Abstract:

    The cell wall of Aspergillus fumigatus contains two Galactose-containing polysaccharides, galactomannan and galactosaminogalactan, whose biosynthetic pathways are not well understood. The A. fumigatus genome contains three genes encoding putative UDP-glucose 4-epimerases, uge3, uge4, and uge5. We undertook this study to elucidate the function of these epimerases. We found that uge4 is minimally expressed and is not required for the synthesis of Galactose-containing exopolysaccharides or Galactose metabolism. Uge5 is the dominant UDP-glucose 4-epimerase in A. fumigatus and is essential for normal growth in Galactose-based medium. Uge5 is required for synthesis of the galactofuranose (Galf) component of galactomannan and contributes Galactose to the synthesis of galactosaminogalactan. Uge3 can mediate production of both UDP-Galactose and UDP-N-acetylgalactosamine (GalNAc) and is required for the production of galactosaminogalactan but not galactomannan. In the absence of Uge5, Uge3 activity is sufficient for growth on Galactose and the synthesis of galactosaminogalactan containing lower levels of Galactose but not the synthesis of Galf. A double deletion of uge5 and uge3 blocked growth on Galactose and synthesis of both Galf and galactosaminogalactan. This study is the first survey of glucose epimerases in A. fumigatus and contributes to our understanding of the role of these enzymes in metabolism and cell wall synthesis.

Jean Marc Nicaud – One of the best experts on this subject based on the ideXlab platform.

  • Awakening the endogenous Leloir pathway for efficient Galactose utilization by Yarrowia lipolytica
    Biotechnology for Biofuels, 2015
    Co-Authors: Zbigniew Lazar, Heber Gamboa-Meléndez, Anne-Marie Crutz- Coq, Cécile Neuvéglise, Jean Marc Nicaud
    Abstract:

    BackgroundProduction of valuable metabolites by Yarrowia lipolytica using renewable raw materials is of major interest for sustainable food and energy. Galactose is a monosaccharide found in galactomannans, hemicelluloses, gums, and pectins.ResultsYarrowia lipolytica was found to express all the Leloir pathway genes for Galactose utilization, which encode fully functional proteins. Gene organization and regulation in Y. lipolytica resembles filamentous fungi rather than Saccharomyces cerevisiae. After Y. lipolytica was grown on mixture of glucose and Galactose, it was then able to metabolize Galactose, including when glucose concentrations were higher than 4 g/L. However, glucose was still the preferred carbon source. Nonetheless, a strain overexpressing the four ylGAL genes of the Leloir pathway was able to efficiently use Galactose as its sole carbon source. This mutant was used to produce citric acid and lipids from Galactose; the yields were comparable to or greater than that obtained for the parental strain (W29) on glucose.ConclusionsThe construction of a Y. lipolytica strain able to produce citric acid and lipids from Galactose is a very important step in bypassing issues related to the use of food-based substrates in industrial applications.