Semi-quantitative comparison of lactophorin in bovine and caprine milks using liquid chromatography/tandem mass spectrometry

Abstract

Lactophorin, also known as glycosylation-dependent cell adhesion molecule 1, is a phosphorylated glycoprotein found in bovine and caprine milks. This protein is located on the milk fat globule membrane (MFGM), with only a weak association to it. Bovine lactophorin exhibits anti-rotavirus and antibacterial activities and provides stable emulsifying properties during milk processing. In this study, a semi-quantitative method for comparing lactophorin levels in bovine and caprine dairy products was developed using liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis of LPLSILK, a shared common proteotypic peptide between the two species. A single prominent LPLSILK peak was clearly detected on multiple reaction monitoring (MRM) chromatograms of tryptic digests from bovine and caprine milk protein extracts, enabling straightforward cross-species comparison based on normalized peak areas. Lactophorin levels were evaluated as normalized LPLSILK peak areas per unit volume (milk) or per unit weight (milk powder), without the use of a stable isotope-labeled internal standard or an external calibration curve. Using this semi-quantitative framework, no statistically significant difference was observed between bovine and caprine milks (P = 0.39). The method was also applicable to milk powders. Future in vitro and in vivo studies are warranted to further examine the biological activities of caprine lactophorin, particularly its potential antimicrobial and antiviral properties.

Keywords

lactophorin / milk / cow / goat / targeted proteomics

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