Glucose transport by mixed ruminal bacteria from a cow.
The glucose transport of mixed ruminal bacteria harvested from a holstein cow fed 5.0 kg of Italian ryegrass and 1.5 kg of flaked corn a day was investigated. The Eadie-Hofstee plot characterized two transport systems: a high-affinity, low-velocity system and a low-affinity, high-velocity system. The former system (K(m) = 16 microM; Vmax = 2.2 nmol/min/mg of protein) is considered dominant under this feeding condition based on the glucose concentration in the rumen (< 1 mM). In light of the facts that the protonophore SF6847 and the lipophilic triphenylmethyl phosphonium ion had no effect on the high-affinity system and an artificially generated proton gradient and electrical potential across the cell membrane did not increase glucose transport, a proton motive force is not be involved in the system. On the other hand, from the facts that chlorhexidine inhibited about 90% of the high-affinity system while iodoacetate showed no significant effect, and a high phosphoenolpyruvate-dependent phosphorylation of glucose was actually shown, the phosphoenolpyruvate-dependent phosphotransferase system is considered the main system in the high-affinity system. Moreover, as shown by the facts that harmaline inhibited about 30% of the high-affinity system and the artificially generated sodium gradient across the cell membrane significantly stimulated glucose transport, this system also includes sodium symport to some degree. The high-affinity system was sensitive to a decrease in pH (< 6.5) and was inhibited by the presence of sucrose, mannose, and fructose.
Kajikawa
H
H
Department of Animal Nutrition, National Institute of Animal Industry, Ibaraki, Japan. kajikawa@niai.affrc.go.jp
Amari
M
M
Masaki
S
S
D000821:Animal Feed; D000818:Animals; D001419:Bacteria / Q000378:metabolism*; D001692:Biological Transport; D001693:Biological Transport, Active; D002417:Cattle; D002710:Chlorhexidine / Q000494:pharmacology; D005260:Female; D005632:Fructose / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism*; D006246:Harmaline / Q000494:pharmacology; D007461:Iodoacetates / Q000494:pharmacology; D019807:Iodoacetic Acid; D008358:Mannose / Q000494:pharmacology; D009570:Nitriles / Q000494:pharmacology; D009861:Onium Compounds / Q000494:pharmacology; D010728:Phosphoenolpyruvate / Q000378:metabolism; D010766:Phosphorylation; D006109:Poaceae / Q000378:metabolism; D017494:Proton Pumps; D012417:Rumen / Q000382:microbiology*; D000254:Sodium-Potassium-Exchanging ATPase; D013395:Sucrose / Q000494:pharmacology; D014320:Triphenylmethyl Compounds / Q000494:pharmacology
D007461:Iodoacetates; D009570:Nitriles; D009861:Onium Compounds; D017494:Proton Pumps; D014320:Triphenylmethyl Compounds; C011561:triphenylmethylphosphonium; D005632:Fructose; C001784:SF 6847; D013395:Sucrose; D010728:Phosphoenolpyruvate; D006246:Harmaline; D000254:Sodium-Potassium-Exchanging ATPase; D005947:Glucose; D008358:Mannose; D002710:Chlorhexidine; D019807:Iodoacetic Acid