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Hexose transport in L6 rat myoblasts. I. Rate‐limiting step, kinetic properties, and evidence for two systems
Author(s) -
D'amore Tony,
Lo Theodore C. Y.
Publication year - 1986
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041270113
Subject(s) - hexose , rate determining step , kinetics , chemistry , biochemistry , limiting , intracellular , sugar , cell , biophysics , enzyme , biology , mechanical engineering , physics , quantum mechanics , engineering , catalysis
The hexose transport system of undifferentiated L6 rat myoblasts was investigated. 2‐Deoxy‐D‐glucose (2‐DOG) and 2‐deoxy‐2‐fluoro‐D‐glucose (2FG) were used as analogues to investigate the rate‐limiting step of hexose uptake into the cell. Virtually all of the 2‐DOG or 2FG taken up into the cell was found to be in the phosphyorylated form. No significant pool of intracellular free sugar could be detected. This demonstrates that hexose transport, not phosphorylation, is the rate‐limiting step. The inhibitory effect of various glucose analogues on 2‐DOG and 3‐O‐methyl‐D‐glucose (3‐OMG) uptake revealed that these two sugars may be taken up into the cell by different carriers. In addition, kinetics analysis of the transport of both sugars also indicates that two hexose transport systems may be present in L6 cells. 2‐DOG is transported by high and low affinity transport systems (K m 0.6 mM and 2.9 mM, respectively), whereas 3‐OMG is transported by a low affinity system (K m 3.5 mM). Treatment of cells with ionophores or energy uncouplers results in inactivation of the high affinity system, but not the low affinity system.