Properties of a Na+/galactose (glucose) symport system in Vibrio parahaemolyticus.
We have investigated galactose transport in a mutant strain of Vibrio parahaemolyticus that lacks a glucose-PTS (phosphoenolpyruvate:carbohydrate phosphotransferase system) and a trehalose-PTS. Cells of the V. parahaemolyticus actively transported D-galactose and Na+ greatly stimulated the transport. Maximum stimulation of D-galactose transport activity was observed at 10mM NaCl, and Na+ could be replaced with Li+. Addition of galactose to the cell suspension under anaerobic conditions elicited Na+ uptake. Therefore, we conclude that this organism accomplishes galactose transport by a Na+/solute symport mechanism. Judging from inhibition results, D-galactose, D-glucose and to a lesser extent alpha-D-fucose are substrates of this transport system. The Na+/galactose symport system exhibited a high affinity for D-galactose (Km: 40 microM) and showed a relatively lower affinity for D-glucose (Km: 420 microM), but the maximum velocities for galactose and glucose transport were almost same (about 52 nmol/min per mg protein). The Na+/D-galactose symport system was induced by either D-galactose or alpha-D-fucose, and repressed by D-glucose.
Sarker
R I
RI
Department of Microbiology, Okayama University, Japan.
Ogawa
W
W
Tsuda
M
M
Tanaka
S
S
Tsuchiya
T
T
D001692:Biological Transport / Q000187:drug effects; D005690:Galactose / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D017136:Ion Transport; D007700:Kinetics; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D012492:Salts / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*; D012965:Sodium Chloride / Q000494:pharmacology; D013379:Substrate Specificity; D014736:Vibrio parahaemolyticus / Q000254:growth & development / Q000378:metabolism*
D009004:Monosaccharide Transport Proteins; D012492:Salts; D012965:Sodium Chloride; D012964:Sodium; D005947:Glucose; D005690:Galactose