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Updated: Oct 5, 2025

Measuring Lactase Enzymatic Activity in the Teaching Lab
Published on: August 6, 2018
Natural Association of Lysozyme and Casein Micelles in Human Milk
Mathias Jaeser1, Ulrike Moeckel1, Kati Weigel1
1Chair of Food Chemistry, Technische Universität Dresden, 01062 Dresden, Germany.
Abstract:
Using reversed phase high-performance liquid chromatography with ultraviolet (UV) detection and electrospray ionization (ESI)-quadrupole time-of-flight mass spectrometry (RP-HPLC-UV-ESI-Q-TOF), the lysozyme content in the milk of 10 volunteering mothers was quantified, ranging from 29 to 96 μg/mL. Following ultracentifugation, it was found that the lysozyme in human milk, unlike other whey proteins, is mainly bound to casein micelles (ca. 75%). The enzymatic activity of human lysozyme, measured as lytic activity against cell walls of Micrococcus lysodeikticus, was similar for the micelle-bound and free protein, indicating that the micellar structure should not affect the antibacterial activity of lysozyme. The results indicate that lysozyme is an integral component of casein micelles in human milk.
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