Transport and phosphorylation of disaccharides by the ruminal bacterium Streptococcus bovis.
Toluene-treated cells of Streptococcus bovis JB1 phosphorylated cellobiose, glucose, maltose, and sucrose by the phosphoenolpyruvate-dependent phosphotransferase system. Glucose phosphorylation was constitutive, while all three disaccharide systems were inducible. Competition experiments indicated that separate phosphotransferase systems (enzymes II) existed for glucose, maltose, and sucrose. [14C]maltose transport was inhibited by excess (10 mM) glucose and to a lesser extent by sucrose (90 and 46%, respectively). [14C]glucose and [14C]sucrose transports were not inhibited by an excess of maltose. Since [14C]maltose phosphorylation in triethanolamine buffer was increased 160-fold as the concentration of Pi was increased from 0 to 100 mM, a maltose phosphorylase (Km for Pi, 9.5 mM) was present, and this activity was inducible. Maltose was also hydrolyzed by an inducible maltase. Glucose 1-phosphate arising from the maltose phosphorylase was metabolized by a constitutive phosphoglucomutase that was specific for alpha-glucose 1-phosphate (Km, 0.8 mM). Only sucrose-grown cells possessed sucrose hydrolase activity (Km, 3.1 mM), and this activity was much lower than the sucrose phosphotransferase system and sucrose-phosphate hydrolase activities.
Martin
S A
SA
Department of Animal Science, Cornell University, Ithaca, New York.
Russell
J B
JB
D000818:Animals; D001692:Biological Transport; D002475:Cellobiose / Q000378:metabolism; D004187:Disaccharides / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D008320:Maltose / Q000378:metabolism; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism; D012417:Rumen / Q000382:microbiology*; D013291:Streptococcus / Q000201:enzymology / Q000378:metabolism*; D013395:Sucrose / Q000378:metabolism
D004187:Disaccharides; D002475:Cellobiose; D013395:Sucrose; D008320:Maltose; D010770:Phosphotransferases; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; D005947:Glucose