The active site composition of porcine pancreatic lipase: possible involvement of lysine.
A mechanism is proposed wherein an essential lysine in porcine pancreatic lipase is the acylable residue in the catalytic mechanism of the enzyme. This mechanism involves an initial interfacial activation step were acylation first takes place in a rate-limiting step on a serine residue assisted by histidine and a carboxyl-containing residue, aspartic acid or glutamic acid, and then in a fast subsequent step the acyl group is transferred to the essential lysine residue at the catalytic site. Indirect support for the mechanism is presented. When the essential lysine is made inactive by reductive methylation, the lipase is functionally converted to a proteinase, as predicted by the mechanism.
Kaimal
T N
TN
Indian Institute of Chemical Technology, CSIR, Hyderabad.
Saroja
M
M
D000478:Alkylation; D000818:Animals; D001665:Binding Sites; D008049:Lipase / Q000032:analysis*; D008239:Lysine / Q000032:analysis*; D010184:Pancreatic Extracts / Q000032:analysis*; D020799:Pancrelipase; D013552:Swine
D010184:Pancreatic Extracts; D020799:Pancrelipase; D008049:Lipase; D008239:Lysine