Effect of beta-lactoglobulin on the activity of pregastric lipase. A possible role for this protein in ruminant milk.
The interaction of bovine beta-lactoglobulin with palmitic and oleic acids has been studied by a partition equilibrium method. Bovine beta-lactoglobulin displays only one high affinity binding site for fatty acids whose association constants for palmitic and oleic acids are 4.2 x 10(6) and 2.3 x 10(6) M-1, respectively. However, other binding sites with low affinity are also present. The existence of one high affinity binding site is in accordance with the amount of fatty acids naturally bound to beta-lactoglobulin isolated from milk. The effect of beta-lactoglobulin on ruminant pregastric lipases from a pharyngeal extract has been assayed. The activity of pharyngeal lipase on a triglyceride emulsion is increased about 200%, 250% and 190% in the presence of 10 mg/ml, 20 mg/ml and 40 mg/ml of beta-lactoglobulin, respectively, the last concentration representing that found physiologically in colostrum. Albumin, another ligand-binding protein, increases the activity of this enzyme to a lesser extent and high levels tend to inhibit enzyme action. These results indicate that beta-lactoglobulin could participate in the digestion of milk lipids during the neonatal period by enhancing the activity of pregastric lipase through removal of the fatty acids that inhibit this enzyme.
Perez
M D
MD
Tecnología y Bioquímica de los Alimentos, Facultad de Veterinaria, Universidad de Zaragoza, Spain.
Sanchez
L
L
Aranda
P
P
Ena
J M
JM
Oria
R
R
Calvo
M
M
D000818:Animals; D002417:Cattle; D004947:Esophagus / Q000201:enzymology*; D005227:Fatty Acids / Q000737:chemistry; D007782:Lactoglobulins / Q000494:pharmacology / Q000502:physiology*; D007820:Laryngeal Mucosa / Q000187:drug effects / Q000201:enzymology*; D008049:Lipase / Q000187:drug effects / Q000378:metabolism*; D008066:Lipolysis; D008892:Milk / Q000201:enzymology*; D010614:Pharynx / Q000201:enzymology*; D012756:Sheep
D005227:Fatty Acids; D007782:Lactoglobulins; D008049:Lipase