Alloxan is an inhibitor of the enzyme O-linked N-acetylglucosamine transferase.
We have previously shown that diabetogenic antibiotic streptozotocin (STZ), an analog of N-acetylglucosamine (GlcNAc), inhibits the enzyme O-GlcNAc-selective N-acetyl-beta-d-glucosaminidase (O-GlcNAcase) which is responsible for the removal of O-GlcNAc from proteins. Alloxan, another beta-cell toxin is a uracil analog. Since the O-GlcNAc transferase (OGT) uses UDP-GlcNAc as a substrate, we investigated whether alloxan might interfere with the process of protein O-glycosylation by blocking OGT, a very abundant enzyme in beta-cells. In isolated pancreatic islets, alloxan almost completely blocked both glucosamine-induced and STZ-induced protein O-GlcNAcylation, suggesting that alloxan indeed was inhibiting (OGT). In order to show definitively that alloxan was inhibiting OGT activity, recombinant OGT was incubated with 0-10 mM alloxan, and OGT activity was measured directly by quantitating UDP-[(3)H]-GlcNAc incorporation into the recombinant protein substrate, nucleoporin p62. Under these conditions, OGT activity was completely inhibited by 1 mM alloxan with half-maximal inhibition achieved at a concentration of 0.1 mM alloxan. Together, these data demonstrate that alloxan is an inhibitor of OGT, and as such, is the first OGT inhibitor described.
Konrad
Robert J
RJ
Department of Diagnostic and Experimental Medicine, Eli Lilly and Company, Indianapolis, IN 46285, USA.
Zhang
Fengxue
F
Hale
John E
JE
Knierman
Michael D
MD
Becker
Gerald W
GW
Kudlow
Jeffrey E
JE
D000496:Alloxan / Q000494:pharmacology*; D000818:Animals; D005944:Glucosamine / Q000494:pharmacology; D006023:Glycoproteins / Q000096:biosynthesis; D006031:Glycosylation; D007515:Islets of Langerhans / Q000201:enzymology*; D007700:Kinetics; D008297:Male; D017351:N-Acetylglucosaminyltransferases / Q000037:antagonists & inhibitors*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013311:Streptozocin / Q000494:pharmacology
D006023:Glycoproteins; D011994:Recombinant Proteins; D013311:Streptozocin; D000496:Alloxan; D017351:N-Acetylglucosaminyltransferases; D005944:Glucosamine