title: Inhibition of lipases by proteins. A kinetic study with dicaprin monolayers.
abstract: We report further investigations on protein inhibition of pancreatic and microbial lipases carried out with the monolayer technique. When beta-lactoglobulin A, melittin, serum albumin, myoglobin, and a protein inhibiting lipase from soybean were preincubated with a dicaprin film at a surface pressure of 35 dynes/cm, no activity was detected with horse pancreatic or Rhizopus delemar lipases. By contrast, Rhizopus arrhizus and Geotrichum candidum lipase activities were not impaired under the same conditions. Experiments using mixed lipid-protein film transfer clearly show that the inhibition of pancreatic lipase is due to the protein associated with lipid and not caused by direct protein-enzyme interaction in the aqueous phase. Three parameters were used to determine the surface properties of the various proteins at the dicaprin/water interface; namely, the initial rate of surface pressure increase, (delta pi/delta t)t = 0, the maximal surface pressure increase, delta pi max, and the critical surface pressure, pi c. A positive correlation was observed between values of (delta pi/delta t)t = 0 of proteins and their respective capacity to inhibit pancreatic and R. delemar lipases. By contrast, there was no apparent correlation with the two other parameters, delta pi max or pi c.
mesh_terms: D000818:Animals; D004075:Diglycerides / Q000378:metabolism*; D005848:Geotrichum / Q000201:enzymology; D005989:Glycerides / Q000378:metabolism*; D006736:Horses; D006868:Hydrolysis; D007700:Kinetics; D007782:Lactoglobulins / Q000494:pharmacology; D008049:Lipase / Q000037:antagonists & inhibitors*; D008555:Melitten / Q000494:pharmacology; D009211:Myoglobin / Q000494:pharmacology; D010179:Pancreas / Q000201:enzymology; D010940:Plant Proteins / Q000494:pharmacology; D011506:Proteins / Q000494:pharmacology*; D012233:Rhizopus / Q000201:enzymology; D012709:Serum Albumin / Q000494:pharmacology; D013025:Glycine max; D013499:Surface Properties; D013552:Swine
chemical_list: D004075:Diglycerides; D005989:Glycerides; D007782:Lactoglobulins; D009211:Myoglobin; D010940:Plant Proteins; D011506:Proteins; D012709:Serum Albumin; C030829:1,3-didecanoylglycerol; C044297:1,2-didecanoylglycerol; D008555:Melitten; D008049:Lipase