Glucose transport and its inhibition by short-chain n-alkanes in Cladosporium resinae.
Glucose transport in Cladosporium resinae was studies with the aid of the non-metabolizable glucose analogue 3-O-methyl-D-glucose (3-O-MG). 3-O-MG, transported as a free sugar without phosphorylation, was found to inhibit glucose uptake competitively. Conversely, glucose was a competitive inhibitor of 3-O-MG uptake. Moreover, both glucose and 3-O-MG were able to bring about rapid counterflow intracellular 3-O-MG. Thus, glucose and 3-O-MG share the same entry and exit systems. The transport of 3-O-MG is carrier mediated and energy dependent as shown by saturation kinetics, strong temperature dependence, accumulation of unaltered 3-O-MG against a concentration gradient, and inhibition of uptake by NaN3, NaCN, and 2,4-dinitrophenol. The glucose transport system appeared to be constitutive for glucose transport in cells grown on fructose, galactose, mannose, xylose, or glucose. There was no derepressible low-Km glucose transport system in C. resinae. n-Hexane and n-heptane were found to inhibit 3-O-MG uptake rapidly at temperatures above 20 C. Over 50% inhibition of the uptake rate occurred after only 10 min of incubation with n-hexane at 30 C. The percentage of inhibition in the presence of n-hexane, compared to controls in the absence of n-hexane, was found to increase with increasing temperature. Longer-chain n-alkanes (C8 to C18) had no significant effect on uptake. The efflux of intracellular 3-O-MG, which appeared to occur by facilitated diffusion, was not affected by any of the n-alkanes tested including n-hexane.
D000473:Alkanes / Q000494:pharmacology*; D001693:Biological Transport, Active / Q000187:drug effects; D002245:Carbon Dioxide / Q000096:biosynthesis; D002250:Carbon Radioisotopes; D002852:Chromatography, Ion Exchange; D002855:Chromatography, Thin Layer; D002963:Cladosporium / Q000378:metabolism*; D003486:Cyanides / Q000494:pharmacology; D003864:Depression, Chemical; D004140:Dinitrophenols / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism*; D007700:Kinetics; D008757:Methylglucosides / Q000378:metabolism; D003904:Mitosporic Fungi / Q000378:metabolism*; D009566:Nitrates / Q000494:pharmacology; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D013696:Temperature
D000473:Alkanes; D002250:Carbon Radioisotopes; D003486:Cyanides; D004140:Dinitrophenols; D008757:Methylglucosides; D009566:Nitrates; D013439:Sulfhydryl Reagents; D002245:Carbon Dioxide; D005947:Glucose