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Endogenous human milk proteolysis as a function of pH

ABSTRACT: The use of human milk products is increasing for high-risk infants. Human milk contains endogenous enzymes that comprise a dynamic proteolytic system; yet, biological properties of these enzymes and their activities in response to variations including pH within infants are unclear. This study was designed to determine the specificity of enzyme-substrate interactions in human milk as a function of pH.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Milk

SUBMITTER: Junai Gan

LAB HEAD: J. Bruce German

PROVIDER: PXD012748 | Pride | 2020-05-26

REPOSITORIES: Pride

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			Action	DRS
	D0.mgf	Mgf
	D0.mzid.gz	Mzid
	D0.raw	Raw
	D2.mgf	Mgf
	D2.mzid.gz	Mzid

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Publications

Selective Proteolysis of α-Lactalbumin by Endogenous Enzymes of Human Milk at Acidic pH.

Gan Junai J Zheng Jingyuan J Krishnakumar Nithya N Goonatilleke Elisha E Lebrilla Carlito B CB Barile Daniela D German J Bruce JB

Molecular nutrition & food research 20190716 18

<h4>Scope</h4>The use of human milk products is increasing for high-risk infants. Human milk contains endogenous enzymes that comprise a dynamic proteolytic system, yet biological properties of these enzymes and their activities in response to variations including pH within infants are unclear. Human milk has a neutral pH around 7, while infant gastric pH varies from 2 to 6 depending on individual conditions. This study is designed to determine the specificity of enzyme-substrate interactions in ...[more]

PMID: 31271254

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RNA-sequencing of the human milk fat layer during colostrum, transitional, and mature stages of lactation

Project description:Human milk fat globules, by enveloping cell contents during their secretion into milk, are a rich source of mammary cell RNA. Here, we pair this non-invasive mRNA source with RNA sequencing technology to probe the milk fat layer transcriptome during three stages of lactation: colostral, transitional, and mature milk production. We find that transcriptional profiles cluster not by postpartum day, but by milk Na:K ratio, indicating that women sampled during the same postpartum time frame could be at markedly different stages of gene expression. Each stage of lactation is characterized by a dynamic range (105-fold) in transcript abundances not previously observed with microarray technology. We discovered that transcripts for isoferritins and cathepsins are strikingly abundant during colostrum production, highlighting the potential importance of these proteins for neonatal health. Two transcripts, encoding M-NM-2-casein (CSN2) and a-lactalbumin (LALBA), make up 45% of the total pool of mRNA in mature lactation. Genes significantly expressed across all stages of lactation are associated with making, modifying, transporting, and packaging milk proteins. Stage-specific transcripts are associated with immune defense during the colostral stage, up-regulation of the machinery needed for milk protein synthesis during the transitional stage, and the production of lipids during mature lactation. We observed strong modulation of key genes involved in lactose synthesis and insulin signaling. In particular, PTPRF may serve as a biomarker linking insulin resistance with insufficient milk supply. This study provides the methodology and reference data set to enable future targeted research on the physiological contributors to sub-optimal lactation in humans. Milk fat mRNA profiles were generated from Day 2 and mature milk samples obtained from lactating mothers

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Human milk and gastric peptidomics

Project description:It is unclear to what degree protein degradation occurs in the infant stomach and whether peptides previously annotated for bioactivity are released. This study combined nanospray liquid chromatography separation with time of flight mass spectrometry, comprehensive structural libraries and informatics to interrogate milk of three human mothers and the gastric aspirates from their 4–12 day post-partum infants. Milk from the mothers contained almost two hundred distinct peptides, demonstrating enzymatic degradation of milk proteins beginning either during lactation or between milk collection and feeding. In the gastric samples, 649 milk peptides were identified, demonstrating that digestion continues in the infant stomach. The majority of peptides in both the intact milk and gastric samples were derived from β-casein. The numbers of peptides from β-casein, lactoferrin, α-lactalbumin, lactadherin, κ-casein, serum albumin, bile-salt associated lipase and xanthine dehydrogenase/oxidase were significantly higher in the gastric samples than the milk samples (p<0.05). Six hundred three peptides were significantly different in abundance between milk and gastric samples (p<0.05). Most of the identified peptides have previously identified biological activity. Gastric proteolysis occurs in the term infant in the first two weeks of life releasing biologically active milk peptides with immunomodulatory, antibacterial, and calcium-binding activity of clinical relevance to the proximal intestinal tract.

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Allergen Shedding in Human Milk from Mothers of Preterm Infants: Proteomic and Peptidomic Feasibility and Pilot Analysis

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Endegenous human milk peptides

Project description:Variations in endogenous peptide profiles, functionality, and the enzymes responsible for the formation of these peptides in human milk are understudied. Additionally, there is a lack of knowledge regarding peptides in donor human milk, which is used to feed preterm infants when mother’s own milk is not (sufficiently) available. To assess this, 29 human milk samples from the Dutch Human Milk Bank were analyzed as three groups, preterm late lactation stage (LS) (n=12), term early (n=8) and term late LS (n=9). Gestational age (GA) groups were defined as preterm (24-36 weeks) and term (>37 weeks). LS was determined as days postpartum as early (16-36 days) or late (55-88 days). Peptides, analyzed by LC-MS/MS, and parent proteins (proteins from matched peptide sequences) were identified and quantified, after which peptide functionality and the enzymes responsible for protein cleavage were determined. A total of 16 different parent proteins were identified from human milk, with no differences by GA or LS. We identified 1104 endogenous peptides, of which, the majority were from the parent proteins β-casein, polymeric immunoglobulin receptor, αs1-casein, osteopontin, and κ-casein. The absolute number of peptide differed by GA and LS with 30 and 41 differing sequences respectively (p<0.05) Odds likelihood tests determined that 32 peptides had a predicted bioactive functionality, with no significant differences between groups. Enzyme prediction analysis showed that plasmin/trypsin enzymes most likely cleaved the identified human milk peptides. These results explain some of the variation in endogenous peptides in human milk, leading to future targets that may be studied for functionality.

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