Specificity and pH dependence for acylproline cleavage by prolidase.
Catalytic pH dependence for the hydrolytic activity of the enzyme prolidase with a series of dipeptide substrates is found to be generally bell-shaped (kcat/Km) or simple sigmoidal (kcat). An enzymic residue with a pKa value of 6.6 is found to be critically involved in the catalytic mechanism, as is the substrate amino group. Significant catalysis at a pH of 6.6 is also observed for prolidase with (alkylthio)acetylprolines and with haloacetylprolines. A reverse-protonation state mechanism for substrate binding and activation is postulated, involving a chelative interaction of the aminoacylamide portion of substrate with a strongly Lewis-acidic active site metal ion.
Mock
W L
WL
Department of Chemistry, University of Illinois, Chicago 60680-4348.
Green
P C
PC
Boyer
K D
KD
D000215:Acylation; D000818:Animals; D002384:Catalysis; D004150:Dipeptidases / Q000378:metabolism*; D004151:Dipeptides / Q000737:chemistry / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D015394:Molecular Structure; D011392:Proline / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D013552:Swine
D004151:Dipeptides; D011392:Proline; D004150:Dipeptidases; C022449:proline dipeptidase