Inhibition of lipases by proteins. A kinetic study with dicaprin monolayers.

L Sarda,C Rivière,A Sugihara,G Pieroni,Y Gargouri,R Verger

doi:10.1016/s0021-9258(18)89549-7

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.

Highlights

For each inhibitory protein, the respective values oE TI,*de,fined as the time needed for the lipase activity to be reduced to half its initial value after protein injection; I, defined as the protein concentration which induces a 50% reduction in the original horse lipase activity; (ArlAt), defined as the initial rate of surface pressure increase occurring after protein injection
In dicaprin film is hydrolyzedby horse pancreatic lipase in sharp the case of R. delemar lipase, no linear correlation was obcontrast with what we have found in the case of mixed served even though Tl/2constantly decreased while (An/At)t=o lipoprotein films maintained at the same surface pressure. increased
D., Charbonnier-Augeire, M., Nalbone, G., Leonardi, J., Hauton, J. c., Pieronl, G., Ferrato, F., and Verger, R

Summary

A KINETIC STUDY WITH DICAPRIN MONOLAYERS*

Youssef GargouriS, GerardPieronis, Claude RiviereQ,Akio SugiharaQ, Louis SardaS, and Robert Verger§. Armax,and the critical surface pressure, re.A communication, further investigations are reported on protein positive correlation was observed between values of inhibition of pancreatic and microbial lipases carried out with (Ar/At),o of proteins and their respective capacity to the monolayer technique. This technique offersunique advaninhibit pancreatic anRd . In thecase of lipolytic enzymes that act on aggregated substrates in an aqueous environment, inhibition studiesare more difficult to perform and to interpret In these investigations, limitations are due to the fact that hydrolysis reaction occurs a t a lipidwater interface where the enzyme binds and tends tounfold and become denatured.

A Monolayer Study

RESULTS

DISCUSSION

AR-1 A R