Characterization of two different types of UDP-glucose/-galactose 4-epimerase involved in galactosylation in fission yeast.
Schizosaccharomyces species are currently the only known organisms with two types of genes encoding UDP-glucose/-galactose 4-epimerase, uge1(+) and gal10(+). A strain deleted for uge1(+) exhibited a severe galactosylation defect and a decrease in activity and in UDP-galactose content when grown in glucose-rich medium (2 % glucose), indicating that Uge1p is a major UDP-glucose/-galactose 4-epimerase under these growth conditions. In contrast, gal10(+) was efficiently expressed and involved in galactosylation of cell-surface proteins in low-glucose medium (0.1 % glucose and 2 % glycerol), but not in galactose-containing medium. In a uge1Deltagal10Delta strain, the galactosylation defect was suppressed and UDP-galactose content restored to wild-type levels in galactose-containing medium. Disruption of gal7(+), encoding galactose-1-phosphate uridylyltransferase, in the uge1Deltagal10Delta strain reversed suppression of the galactosylation defect and reduced levels of UDP-galactose, indicating that galactose is transported from the medium to the cytosol and is converted into UDP-galactose via galactose 1-phosphate by Gal7p in Sch. pombe.
Suzuki
Shotaro
S
Department of Applied Biological Sciences, Faculty of Agriculture, Kagawa University, Miki-cho, Kagawa 761-0795, Japan.
Matsuzawa
Tomohiko
T
Department of Applied Biological Sciences, Faculty of Agriculture, Kagawa University, Miki-cho, Kagawa 761-0795, Japan.
Nukigi
Yayoi
Y
Department of Applied Biological Sciences, Faculty of Agriculture, Kagawa University, Miki-cho, Kagawa 761-0795, Japan.
Takegawa
Kaoru
K
Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University, 6-10-1 Hakozaki, Fukuoka 812-8581, Japan.
Tanaka
Naotaka
N
Department of Applied Biological Sciences, Faculty of Agriculture, Kagawa University, Miki-cho, Kagawa 761-0795, Japan.
D005695:Galactosephosphates / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D012568:Schizosaccharomyces / Q000201:enzymology* / Q000235:genetics; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*; D014534:UDPglucose 4-Epimerase / Q000235:genetics / Q000378:metabolism*; D014531:Uridine Diphosphate Galactose / Q000378:metabolism
D005695:Galactosephosphates; D029702:Schizosaccharomyces pombe Proteins; C029973:galactose-1-phosphate; D014531:Uridine Diphosphate Galactose; D014534:UDPglucose 4-Epimerase