title: Inhibition of plasmin by beta-lactoglobulin using casein and a synthetic substrate.
abstract: Bovine plasmin (EC 3.4.21.7) activity was measured on H-D-valyl-L-leucyl-L-lysyl-4-nitroanilide and acid casein in the presence of native and heat-denatured beta-lactoglobulin (denatured at 100 degrees C for 15 min before being mixed with plasmin solutions). Native or denatured beta-lactoglobulin was then heated with plasmin at 60 degrees C for 15 min. Enzyme activity again was estimated after this mild heat treatment. Native and denatured beta-lactoglobulin inhibited the action of plasmin on H-D-valyl-L-leucyl-L-lysyl-4-nitroanilide and casein. The mild heat treatment (60 degrees C for 15 min) caused stronger inhibition of the activity of plasmin against casein and the synthetic substrate. For H-D-valyl-L-leucyl-L-lysyl-4-nitroanilide, inhibition was competitive in unheated mixtures, but heating beta-lactoglobulin with plasmin changed inhibition type to mixed. This change suggests a heat-dependent interaction between plasmin and beta-lactoglobulin. Native beta-lactoglobulin was more inhibitory of plasmin's action against casein than was denatured beta-lactoglobulin. The converse was observed when plasmin activity was measured with the synthetic substrate.
authors.affiliation: Department of Nutrition and Food Sciences, Utah State University, Logan 84322-8700.
authors.forename: E D
authors.initials: ED
authors.lastname: Bastian
authors.forename: K G
authors.initials: KG
authors.lastname: Hansen
authors.forename: R J
authors.initials: RJ
authors.lastname: Brown
mesh_terms: D000818:Animals; D002364:Caseins / Q000378:metabolism*; D002417:Cattle; D005341:Fibrinolysin / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006358:Hot Temperature; D007700:Kinetics; D007782:Lactoglobulins / Q000008:administration & dosage / Q000494:pharmacology*; D008823:Micelles; D009842:Oligopeptides / Q000378:metabolism; D011489:Protein Denaturation
chemical_list: D002364:Caseins; D007782:Lactoglobulins; D008823:Micelles; D009842:Oligopeptides; C018788:valyl-leucyl-lysine 4-nitroanilide; D005341:Fibrinolysin