Alloxan is an inhibitor of O-GlcNAc-selective N-acetyl-beta-D-glucosaminidase.
We have previously shown that streptozotocin (STZ) inhibits O-GlcNAc-selective N-acetyl-beta-d-glucosaminidase (O-GlcNAcase), the enzyme that removes O-GlcNAc from proteins. In light of this observation, we explored the possibility that the diabetogenic toxin alloxan, an O-GlcNAc transferase (OGT) inhibitor, might also inhibit O-GlcNAcase. Alloxan inhibited islet O-GlcNAcase with a dose-response much like that of STZ. Similar to STZ, islet O-GlcNAcase was more susceptible to alloxan inhibition than was brain O-GlcNAcase. Alloxan directly inhibited recombinant O-GlcNAcase activity with a dose-response very similar to that of STZ. Subsequent LC/MS/MS analysis revealed that alloxan modified the tryptic digest pattern of the enzyme. One tryptic peptide LGCFEIAK(894-901) was modified by alloxan. Two other tryptic peptides, LDQVSQFGCR(158-167) and SFALLFDDIDHNMCAADK(168-185), both N-terminal active site peptides, were absent after alloxan treatment. Together, these data demonstrate that alloxan is an inhibitor of O-GlcNAc-selective N-acetyl-beta-d-glucosaminidase, with inhibition corresponding to an altered tryptic digest pattern of N-terminal active site peptides.
Lee
Thomas N
TN
Eli Lilly and Company, Indianapolis, IN 46285, USA.
Alborn
William E
WE
Knierman
Michael D
MD
Konrad
Robert J
RJ
D000496:Alloxan / Q000008:administration & dosage*; D000818:Animals; D001921:Brain / Q000187:drug effects* / Q000201:enzymology*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D007515:Islets of Langerhans / Q000187:drug effects* / Q000201:enzymology*; D051381:Rats; D001619:beta-N-Acetylhexosaminidases / Q000037:antagonists & inhibitors* / Q000378:metabolism*
D000496:Alloxan; C110628:hexosaminidase C; D001619:beta-N-Acetylhexosaminidases