title: Interaction of 5-oxo-L-prolinase with nucleoside triphosphates. Evidence suggesting substrate-dependent conformational change.
abstract: 5-Oxoprolinase catalyzes the coupled hydrolysis of ATP and 5-oxoproline to yield glutamate, ADP, and Pi; the reaction may be partially or completely uncoupled by structural modification of either substrate. In the present work, we found slow 5-oxoproline-dependent changes in the rates of hydrolysis of ITP, GTP, and UTP. For example, in the absence of 5-oxoproline, the enzyme catalyzes the hydrolysis of UTP at a rapid and constant rate. Following addition of 5-oxo-L-proline, the rate of hydrolysis decreases slowly; after about 25 min, a much slower and constant rate of hydrolysis is attained. This change in rate is associated with a decrease in Vmax and an increase in the Km for UTP. In similar studies with ATP, both Vmax and Km increase over a much shorter time period (less than 10 s). The findings indicate that 5-oxoprolinase is a hysteretic enzyme, and are consistent with the hypothesis that in the normal catalytic reaction, the binding of both ATP and 5-oxo-proline to the enzyme induces a conformational change that brings the substrates into a juxtaposition that facilitates the reaction.
mesh_terms: D000581:Amidohydrolases / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D020558:GTP Phosphohydrolases / Q000037:antagonists & inhibitors; D007668:Kidney / Q000201:enzymology; D007700:Kinetics; D011485:Protein Binding; D011487:Protein Conformation; D011752:Pyroglutamate Hydrolase / Q000378:metabolism*; D051381:Rats; D012265:Ribonucleotides; D013329:Structure-Activity Relationship
chemical_list: D012265:Ribonucleotides; D000581:Amidohydrolases; D011752:Pyroglutamate Hydrolase; D020558:GTP Phosphohydrolases