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Proteomic profiling of microbial transglutaminase-induced polymerization of milk proteins
1Department of Food Science, Fu Jen Catholic University, Xin Zhuang, Taipei 242, Taiwan. 075101@mail.fju.edu.tw
Abstract:
Microbial transglutaminase (MTGase)-induced polymerization of individual milk proteins during incubation was investigated using a proteomics-based approach. The addition of MTGase (0.25-2.0 units/mL) caused the milk proteins to polymerize after a 3-h incubation period. Sodium dodecyl sulfate-PAGE analysis showed that the total intensities of the protein bands that corresponded to α(S)-casein, β-casein, and κ-casein decreased from 8,245.6, 6,677.2, and 586.6 arbitrary units to 1,911.7, 0.0, and 66.2 arbitrary units, respectively. Components with higher molecular weights were observed, and the intensity of these proteins increased after 3h of incubation. These results support that inter- or intramolecular crosslinking occurred in the casein proteins of MTGase-treated milk. Two-dimensional electrophoresis analysis indicated that isomers of β-casein, κ-casein, a fraction of serum albumin, α(S1)-casein, α(S2)-casein, β-lactoglobulin, and α-lactalbumin in the milk were polymerized following incubation with MTGase. In addition, MTGase-induced polymerization occurred earlier for β-casein and κ-casein isomers than for other milk proteins.
Insights
Microbial transglutaminase (MTGase) causes milk proteins, especially caseins, to polymerize within 3 hours. This enzyme-induced crosslinking creates higher molecular weight protein components, altering milk
Area of Science:
- Food Science
- Biochemistry
- Proteomics
Background:
- Milk proteins undergo various modifications affecting their functional properties.
- Enzymatic crosslinking is a key process in food modification.
- Microbial transglutaminase (MTGase) is known to crosslink proteins.
Purpose of the Study:
- To investigate MTGase-induced polymerization of milk proteins.
- To identify specific milk proteins affected by MTGase.
- To determine the timeline of MTGase-mediated protein polymerization.
Main Methods:
- Proteomics-based approach.
- Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).
- Two-dimensional electrophoresis (2D-PAGE).
Main Results:
- MTGase addition (0.25-2.0 units/mL) induced milk protein polymerization after 3 hours.
- SDS-PAGE showed significant decreases in α(S)-casein, β-casein, and κ-casein band intensities.
- Higher molecular weight protein components increased, indicating inter- or intramolecular crosslinking, particularly in casein proteins.
- 2D-PAGE confirmed polymerization of various milk proteins including casein isomers, serum albumin, β-lactoglobulin, and α-lactalbumin.
- Polymerization initiated earlier for β-casein and κ-casein isomers.
Conclusions:
- MTGase effectively induces polymerization of milk proteins, primarily caseins.
- The crosslinking process involves both inter- and intramolecular reactions.
- MTGase exhibits differential activity, with faster polymerization observed for β-casein and κ-casein isomers.
