Glycosylasparaginase inhibition studies: competitive inhibitors, transition state mimics, noncompetitive inhibitors.
Glycosylasparaginase catalyzes the hydrolysis of the N-glycosylic bond between asparagine and N-acetylglucosamine in the catabolism of N-linked glycoproteins. Previously only three competitive inhibitors, one noncompetitive inhibitor, and one irreversible inhibitor of glycosylasparaginase activity had been reported. Using human glycosylasparaginase from human amniotic fluid, L-aspartic acid and four of its analogues, where the alpha-amino group was substituted with a chloro, bromo, methyl or hydrogen, were competitive inhibitors having Ki values between 0.6-7.7 mM. These results provide supporting evidence for a proposed intramolecular autoproteolytic activation reaction. A proposed phosphono transition state mimic and a sulfo transition state mimic were competitive inhibitors with Ki values 0.9 mM and 1.4 mM, respectively. These results support a mechanism for the enzyme-catalyzed reaction involving formation of a tetrahedral high-energy intermediate. Three analogues of the natural substrate were noncompetitive inhibitors with Ki values between 0.56-0.75 mM, indicating the presence of a second binding site that may recognize (substituted)acetamido groups.
Risley
J M
JM
Department of Chemistry, University of North Carolina at Charlotte, Charlotte, NC 28223, USA. jmrisley@email.uncc.edu
Huang
D H
DH
Kaylor
J J
JJ
Malik
J J
JJ
Xia
Y Q
YQ
D000117:Acetylglucosamine / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism*; D001227:Aspartylglucosylaminase / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D003545:Cysteine / Q000737:chemistry / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D015394:Molecular Structure; D011422:Propionates / Q000737:chemistry / Q000378:metabolism; D012697:Serine Endopeptidases / Q000737:chemistry / Q000378:metabolism
D004791:Enzyme Inhibitors; D011422:Propionates; C000009:N-acetylglucosaminylasparagine; D001224:Aspartic Acid; D012697:Serine Endopeptidases; D001227:Aspartylglucosylaminase; D003545:Cysteine; D000117:Acetylglucosamine