melitten and 1-3-didecanoylglycerol

The effects of several proteins on the hydrolysis at pH 3.0 of didecanoylglycerol monolayers by human gastric lipase were investigated. Among the six proteins tested (bovine serum albumin, myoglobin, a protein inhibiting lipase isolated from soya bean, melittin, beta-lactoglobulin and ovalbumin), only the first three proteins were found to inhibit lipase activity. The inhibition capacity of the proteins was not related to the decrease in interfacial tension or to their isoelectric points. However, inhibition of human gastric lipase by proteins may be correlated with the penetration power of the protein into the lipid interface. It is hypothesized that this lipase has a higher penetration power than that of pancreatic lipase, even though the former enzyme is more susceptible to interfacial denaturation.

Topics: Diglycerides; Gastric Juice; Humans; Hydrogen-Ion Concentration; Hydrolysis; Lactoglobulins; Lipase; Lipolysis; Melitten; Myoglobin; Ovalbumin; Pancreas; Plant Proteins, Dietary; Pressure; Serum Albumin, Bovine; Soybean Proteins; Substrate Specificity; Surface Properties

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.

Topics: Animals; Diglycerides; Geotrichum; Glycerides; Glycine max; Horses; Hydrolysis; Kinetics; Lactoglobulins; Lipase; Melitten; Myoglobin; Pancreas; Plant Proteins; Proteins; Rhizopus; Serum Albumin; Surface Properties; Swine