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Differential roles of the Leloir pathway enzymes and metabolites in defining galactose sensitivity in yeast.
Mol Genet Metab. 2004 Sep-Oct; 83(1-2):103-16.MG

Abstract

The metabolism of galactose via enzymes of the Leloir pathway: galactokinase, galactose-1-P uridylyltransferase, and UDP galactose-4'-epimerase, is a process that has been conserved from Escherichia coli through humans. Impairment of this pathway in patients results in the disease galactosemia. Despite decades of study, the underlying pathophysiology in galactosemia remains unknown. Here we have defined the functional and metabolic implications of impaired galactose metabolism in yeast, by asking two questions: (1) What is the impact of loss of each of the three Leloir enzymes on the ability of cells to metabolize galactose, and on their sensitivity to galactose, and (2) what is the relationship between gal-1P and galactose-sensitivity in yeast? Our results demonstrate that only transferase-null cells are able to deplete their medium of galactose; deletion of kinase or epimerase halts this process. In contrast, only kinase-null cultures grow well in glycerol/ethanol medium despite the addition of galactose; both transferase and epimerase-null yeast arrest growth under these conditions. Indeed, epimerase-null yeast arrest growth at galactose concentrations 10-fold lower than do their transferase-null counterparts. Secondary deletion of kinase relieves growth arrest in both strains. Finally, rather than a continuous relationship between gal-1P and growth arrest, we observed a threshold level of gal-1P (approximately 10 nmol/mg cell DM) above which both transferase-null and epimerase-null cultures could not grow. These results both confirm and significantly extend prior knowledge of galactose metabolism in yeast, and set the stage for future studies into the mediators and mechanism of Leloir-impaired galactose sensitivity in eukaryotes.

Authors+Show Affiliations

Department of Human Genetics, Emory University School of Medicine, Emory University, Atlanta, GA 30322, USA.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

15464425

Citation

Ross, Kerry L., et al. "Differential Roles of the Leloir Pathway Enzymes and Metabolites in Defining Galactose Sensitivity in Yeast." Molecular Genetics and Metabolism, vol. 83, no. 1-2, 2004, pp. 103-16.
Ross KL, Davis CN, Fridovich-Keil JL. Differential roles of the Leloir pathway enzymes and metabolites in defining galactose sensitivity in yeast. Mol Genet Metab. 2004;83(1-2):103-16.
Ross, K. L., Davis, C. N., & Fridovich-Keil, J. L. (2004). Differential roles of the Leloir pathway enzymes and metabolites in defining galactose sensitivity in yeast. Molecular Genetics and Metabolism, 83(1-2), 103-16.
Ross KL, Davis CN, Fridovich-Keil JL. Differential Roles of the Leloir Pathway Enzymes and Metabolites in Defining Galactose Sensitivity in Yeast. Mol Genet Metab. 2004 Sep-Oct;83(1-2):103-16. PubMed PMID: 15464425.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Differential roles of the Leloir pathway enzymes and metabolites in defining galactose sensitivity in yeast. AU - Ross,Kerry L, AU - Davis,Charity N, AU - Fridovich-Keil,Judith L, PY - 2004/04/23/received PY - 2004/07/04/revised PY - 2004/07/07/accepted PY - 2004/10/7/pubmed PY - 2005/3/22/medline PY - 2004/10/7/entrez SP - 103 EP - 16 JF - Molecular genetics and metabolism JO - Mol Genet Metab VL - 83 IS - 1-2 N2 - The metabolism of galactose via enzymes of the Leloir pathway: galactokinase, galactose-1-P uridylyltransferase, and UDP galactose-4'-epimerase, is a process that has been conserved from Escherichia coli through humans. Impairment of this pathway in patients results in the disease galactosemia. Despite decades of study, the underlying pathophysiology in galactosemia remains unknown. Here we have defined the functional and metabolic implications of impaired galactose metabolism in yeast, by asking two questions: (1) What is the impact of loss of each of the three Leloir enzymes on the ability of cells to metabolize galactose, and on their sensitivity to galactose, and (2) what is the relationship between gal-1P and galactose-sensitivity in yeast? Our results demonstrate that only transferase-null cells are able to deplete their medium of galactose; deletion of kinase or epimerase halts this process. In contrast, only kinase-null cultures grow well in glycerol/ethanol medium despite the addition of galactose; both transferase and epimerase-null yeast arrest growth under these conditions. Indeed, epimerase-null yeast arrest growth at galactose concentrations 10-fold lower than do their transferase-null counterparts. Secondary deletion of kinase relieves growth arrest in both strains. Finally, rather than a continuous relationship between gal-1P and growth arrest, we observed a threshold level of gal-1P (approximately 10 nmol/mg cell DM) above which both transferase-null and epimerase-null cultures could not grow. These results both confirm and significantly extend prior knowledge of galactose metabolism in yeast, and set the stage for future studies into the mediators and mechanism of Leloir-impaired galactose sensitivity in eukaryotes. SN - 1096-7192 UR - https://www.unboundmedicine.com/medline/citation/15464425/Differential_roles_of_the_Leloir_pathway_enzymes_and_metabolites_in_defining_galactose_sensitivity_in_yeast_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S1096-7192(04)00177-5 DB - PRIME DP - Unbound Medicine ER -