Human gastric lipase. The N-terminal tetrapeptide is essential for lipid binding and lipase activity.
Human gastric lipase subjected to limited tryptic proteolysis lost its ability to hydrolyze emulsified long-chain triacylglycerol. Activity against a water-soluble substrate was however retained, indicating that proteolysis did not affect the active site. Sequence analysis revealed that trypsin specifically cleaved the linkage between lysine-4 and leucine-5. This cleavage rendered the enzyme unable to bind to emulsified triacylglycerol particles, e.g. human milk fat globules. We suggest that the N-terminal tetrapeptide, in particular lysine-4, is essential for the binding of human gastric lipase to lipid/water interfaces, and hence, for its physiological function.
Bernbäck
S
S
Department of Physiological Chemistry, University of Umeå, Sweden.
Bläckberg
L
L
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D001665:Binding Sites; D004591:Electrophoresis, Polyacrylamide Gel; D005223:Fats / Q000032:analysis; D005750:Gastric Juice / Q000201:enzymology*; D006801:Humans; D006868:Hydrolysis; D008049:Lipase / Q000032:analysis* / Q000502:physiology; D008055:Lipids / Q000032:analysis*; D008895:Milk, Human / Q000032:analysis; D008969:Molecular Sequence Data; D015394:Molecular Structure; D014357:Trypsin
D000596:Amino Acids; D005223:Fats; D008055:Lipids; D008049:Lipase; D014357:Trypsin