J. Biol. Chem., Vol. 261, Issue 6, 2542-2547, 02, 1986
Photoaffinity labeling of glyceraldehyde-3-phosphate dehydrogenase by an aryl azide derivative of glucosamine in human erythrocytes
JM May
An aryl azide derivative of glucosamine, N-(4-iodoazidosalicyl)-2-amido-
2-deoxy-D-glucopyranose (GlcNAs), was synthesized as a potential
photoaffinity label for the facilitative hexose carrier. The derivative
inhibited hexose uptake into intact human erythrocytes half-maximally at
3.5 mM and was itself slowly transported into cells. However, photolysis of
iodinated GlcNAs with leaky erythrocyte ghosts produced appreciable
labeling on gel electrophoresis only of Band 6, which is
glyceraldehyde-3-phosphate dehydrogenase. Band 6 photolabeling in leaky
ghosts by GlcNAs was: saturable, due mostly to the aryl azide moiety,
inhibited by agents with known affinity for the enzyme including sulfhydryl
reagents and the enzyme substrate glyceraldehyde-3- phosphate, and not
inhibited by the free-radical scavenger p- aminobenzoic acid. Moreover,
GlcNAs also inhibited erythrocyte glyceraldehyde-3-phosphate dehydrogenase
activity in a dose-dependent fashion in the dark and more potently
following irradiation. In resealed ghosts, Band 6 labeling was decreased by
D-glucose, reflecting inhibition of carrier-mediated uptake of the agent.
GlcNAs appears to be a specific photoaffinity label for erythrocyte
glyceraldehyde-3- phosphate dehydrogenase, and therefore potentially useful
for studies of enzyme activity, compartmentation, or membrane association.