Effects of genetic variants and sialylation on in vitro digestibility of purified κ-casein
(2022) In Journal of Dairy Science 105(4). p.2803-2814- Abstract
Milk with different κ-casein (CN) phenotypes has previously been found to influence its gastric digestion rate. Therefore, the aim of the present study is to disentangle contributions of genetic variation and its related sialylation on the in vitro digestion process of κ-CN. Accordingly, κ-CN was purified from milk representing homozygous cows with κ-CN phenotypes AA, BB, or EE and used as substrate molecules in model studies using the INFOGEST 2.0 in vitro static digestion model. Furthermore, the effect of removal of the terminal sialic acids present on the O-linked oligosaccharides of the purified κ-CN A, B, and E protein variants were studied by desialylation enzymatic assays. The κ-CN proteins were purified by reducing anion... (More)
Milk with different κ-casein (CN) phenotypes has previously been found to influence its gastric digestion rate. Therefore, the aim of the present study is to disentangle contributions of genetic variation and its related sialylation on the in vitro digestion process of κ-CN. Accordingly, κ-CN was purified from milk representing homozygous cows with κ-CN phenotypes AA, BB, or EE and used as substrate molecules in model studies using the INFOGEST 2.0 in vitro static digestion model. Furthermore, the effect of removal of the terminal sialic acids present on the O-linked oligosaccharides of the purified κ-CN A, B, and E protein variants were studied by desialylation enzymatic assays. The κ-CN proteins were purified by reducing anion exchange chromatography with purities of variants A, B, and E of 93.0, 97.1, and 90.0%, respectively. Protein degradations of native and desialylated κ-CN isolates in gastric and intestinal phases were investigated by sodium dodecyl sulfate-PAGE, degree of hydrolysis (DH), and liquid chromatography electrospray ionization mass spectrometry. It was shown that after purification, the κ-CN molecules reassembled into multimer states, which then constituted the basis for the digestion studies. As assessed by DH, purified variants A and E were found to exhibit faster in vitro digestion rates in both gastric and intestinal phases compared with variant B. Desialylation increased both gastric and intestinal digestion rates for all variants, as measured by DH. In the gastric phase, desialylation promoted digestion of variant B at a rate comparable with native variants A and E, whereas in the intestinal phase, desialylation of variant B promoted better digestion than native A or E. Taken together, the results confirm that low glycosylation degree of purified κ-CN promotes faster in vitro digestion rates, and that desialylation of the O-linked oligosaccharides further promotes digestion. This finding could be applied to produce dairy products with enhanced digestibility.
(Less)
- author
- Sheng, Bulei ; Nielsen, Søren D. ; Glantz, Maria LU ; Paulsson, Marie LU ; Poulsen, Nina A. and Larsen, Lotte B.
- organization
- publishing date
- 2022-04
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- degree of hydrolysis, digestion rate, glycosylation, sialic acid
- in
- Journal of Dairy Science
- volume
- 105
- issue
- 4
- pages
- 12 pages
- publisher
- American Dairy Science Association
- external identifiers
-
- pmid:35151483
- scopus:85124422363
- ISSN
- 0022-0302
- DOI
- 10.3168/jds.2021-21289
- language
- English
- LU publication?
- yes
- additional info
- Publisher Copyright: © 2022 American Dairy Science Association
- id
- 4cfad827-0f90-4040-bf46-347d76611973
- date added to LUP
- 2022-12-30 14:20:11
- date last changed
- 2024-04-15 00:09:42
@article{4cfad827-0f90-4040-bf46-347d76611973,
abstract = {{<p>Milk with different κ-casein (CN) phenotypes has previously been found to influence its gastric digestion rate. Therefore, the aim of the present study is to disentangle contributions of genetic variation and its related sialylation on the in vitro digestion process of κ-CN. Accordingly, κ-CN was purified from milk representing homozygous cows with κ-CN phenotypes AA, BB, or EE and used as substrate molecules in model studies using the INFOGEST 2.0 in vitro static digestion model. Furthermore, the effect of removal of the terminal sialic acids present on the O-linked oligosaccharides of the purified κ-CN A, B, and E protein variants were studied by desialylation enzymatic assays. The κ-CN proteins were purified by reducing anion exchange chromatography with purities of variants A, B, and E of 93.0, 97.1, and 90.0%, respectively. Protein degradations of native and desialylated κ-CN isolates in gastric and intestinal phases were investigated by sodium dodecyl sulfate-PAGE, degree of hydrolysis (DH), and liquid chromatography electrospray ionization mass spectrometry. It was shown that after purification, the κ-CN molecules reassembled into multimer states, which then constituted the basis for the digestion studies. As assessed by DH, purified variants A and E were found to exhibit faster in vitro digestion rates in both gastric and intestinal phases compared with variant B. Desialylation increased both gastric and intestinal digestion rates for all variants, as measured by DH. In the gastric phase, desialylation promoted digestion of variant B at a rate comparable with native variants A and E, whereas in the intestinal phase, desialylation of variant B promoted better digestion than native A or E. Taken together, the results confirm that low glycosylation degree of purified κ-CN promotes faster in vitro digestion rates, and that desialylation of the O-linked oligosaccharides further promotes digestion. This finding could be applied to produce dairy products with enhanced digestibility.</p>}},
author = {{Sheng, Bulei and Nielsen, Søren D. and Glantz, Maria and Paulsson, Marie and Poulsen, Nina A. and Larsen, Lotte B.}},
issn = {{0022-0302}},
keywords = {{degree of hydrolysis; digestion rate; glycosylation; sialic acid}},
language = {{eng}},
number = {{4}},
pages = {{2803--2814}},
publisher = {{American Dairy Science Association}},
series = {{Journal of Dairy Science}},
title = {{Effects of genetic variants and sialylation on in vitro digestibility of purified κ-casein}},
url = {{http://dx.doi.org/10.3168/jds.2021-21289}},
doi = {{10.3168/jds.2021-21289}},
volume = {{105}},
year = {{2022}},
}