Effects of Native and Denatured Whey Proteins on Plasminogen Activator Activity

The plasmin system native to bovine milk consists of the caseinolytic serine proteinase plasmin; its inactive zymogen, plasminogen; plasminogen activators; and inhibitors. Evidence in the literature indicates that whey proteins may inhibit plasmin activity, but there is very little mention of their...

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Bibliographic Details
Published in:Journal of dairy science 2004-08, Vol.87 (8), p.2344-2350
Main Authors: Rippel, K.M., Nielsen, S.S., Hayes, K.D.
Format: Article
Language:English
Subjects:
Animal productions
assays
Biological and medical sciences
bovine serum albumin
denaturation
enzyme activity
enzyme inhibition
enzyme kinetics
enzyme substrates
Fibrinolysin - metabolism
Food industries
Fundamental and applied biological sciences. Psychology
Hot Temperature
Kinetics
lactalbumin
Lactalbumin - pharmacology
lactoglobulins
Lactoglobulins - pharmacology
Milk and cheese industries. Ice creams
Milk Proteins - chemistry
Milk Proteins - pharmacology
Oligopeptides - metabolism
plasmin
Plasminogen - metabolism
plasminogen activator
Plasminogen Activators - metabolism
protein degradation
Protein Denaturation
Structure-Activity Relationship
substrate specificity
Terrestrial animal productions
Vertebrates
whey protein
Whey Proteins
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Summary:The plasmin system native to bovine milk consists of the caseinolytic serine proteinase plasmin; its inactive zymogen, plasminogen; plasminogen activators; and inhibitors. Evidence in the literature indicates that whey proteins may inhibit plasmin activity, but there is very little mention of their effect on plasminogen activators. The objective of this research was to determine the effect of both unheated and heat-denatured β-lactoglobulin (β-LG), α-lactalbumin (α-LA), and BSA on plasminogen activators. Plasminogen activator activity was significantly stimulated by non-heat treated and denatured α-LA as well as by denatured β-LG. The stimulation effect by these whey proteins was kinetically characterized, which showed that all 3 significantly increased the rate of plasminogen activation. The stimulation effect was shown to be independent of any effect of the whey proteins on plasmin activity by testing 2 different substrates, d-Val-Leu-Lys p-nitroanilide (S-2251) and Spectrozyme PL (Spec PL), in a plasmin assay. Results using S-2251 confirmed the inhibitory effect of whey proteins on plasmin observed by several researchers. However, use of SpecPL did not suggest inhibition. Ligand binding studies showed this discrepancy to be due to significant interaction between S-2251 and the whey proteins. Overall, this study indicates that whey protein incorporation into cheese may not hinder plasmin activity and may stimulate plasminogen activation. Furthermore, the results indicate the need for careful consideration of the type of synthetic substrate chosen for model work involving whey proteins and the plasmin system.
ISSN:0022-0302
1525-3198
DOI:10.3168/jds.S0022-0302(04)73356-1