Enzymes In Human Milk Research Articles

Macronutrient Digestion and Absorption in the Preterm Infant.

The human fetus receives oral nutrition through swallowed amniotic fluid and this makes a significant nutritional contribution to the fetus. Postnatally, macronutrient absorption and digestion appear to function well in the preterm infant. Although pancreatic function is relatively poor, the newborn infant has several mechanisms to overcome this. These include a range of digestive enzymes in human milk, novel digestive enzymes involved in fat and protein digestion that do not appear to be present in the older child or adult, and the presence of a Bifidobacterium-rich colonic microbiome that may "scavenge" unabsorbed macronutrients and make them available to the infant.

Enzymes in Human Milk.

Milk proteins are a complex and diverse source of biological activities. Beyond their function, intact milk proteins also act as carriers of encrypted functional sequences that, when released as peptides, exert biological functions, including antimicrobial and immunomodulatory activity, which could contribute to the infant's competitive success. Research has now revealed that the release of these functional peptides begins within the mammary gland itself. A complex array of proteases produced in mother's milk has been shown to be active in the milk, releasing these peptides. Moreover, our recent research demonstrates that these milk proteases continue to digest milk proteins within the infant's stomach, possibly even to a larger extent than the infant's own proteases. As the neonate has relatively low digestive capacity, the activity of milk proteases in the infant may provide important assistance to digesting milk proteins. The coordinated release of these encrypted sequences is accomplished by selective proteolytic action provided by an array of native milk proteases and infant-produced enzymes. The task for scientists is now to discover the selective advantages of this protein-protease-based peptide release system.

Digestive enzymes in human milk: stability at suboptimal storage temperatures.

Women who return to work outside of the home while still breastfeeding must often store the expressed milk at less than optimal temperatures. Human milk provides digestive enzymes (amylase and lipase) that compensate in the newborn for immature pancreatic function. We have assessed the stability of amylase and bile salt-dependent lipase after storage for 1-24 h at 15, 25, and 38 degrees C. Both enzymes were stable at 15 and 25 degrees C for 24 h, whereas at 38 degrees C there was a 15 and 20% decrease in lipase and amylase activity, respectively. The stability of milk lipoprotein lipase was also tested. This very labile enzyme was more stable in milk than previously reported for blood and tissues, i.e., 20 and 50% decrease in activity after storage at 15 or 25 degrees C for 24 h, respectively. A two-unit drop in milk pH by 24 h of storage would not affect the activity of digestive enzymes, which are stable at pH > 3.5. We conclude that milk provides the same compensatory digestive activity after short-term storage, even at relatively high temperature, as when fed fresh to the infant.

Digestive Enzymes in Human Milk: Stability at Suboptimal Storage Temperatures

Background:Women who return to work outside of the home while still breastfeeding must often store the expressed milk at less than optimal temperatures. Human milk provides digestive enzymes (amylase and lipase) that compensate in the newborn for immature pancreatic function.Methods:We have assessed the stability of amylase and bile salt‐dependent lipase after storage for 1‐24 h at 15, 25, and 38°C.Results:Both enzymes were stable at 15 and 25°C for 24 h, whereas at 38°C there was a 15 and 20% decrease in lipase and amylase activity, respectively. The stability of milk lipoprotein lipase was also tested. This very labile enzyme was more stable in milk than previously reported for blood and tissues, i.e., 20 and 50% decrease in activity after storage at 15 or 25°C for 24 h, respectively. A two‐unit drop in milk pH by 24 h of storage would not affect the activity of digestive enzymes, which are stable at pH >3.5.Conclusions:We conclude that milk provides the same compensatory digestive activity after short‐term storage, even at relatively high temperature, as when fed fresh to the infant.

Role and significance of enzymes in human milk

Although human milk generally contains higher levels of enzymes than bovine milk, little definitive information is available concerning their role or significance. The enzyme levels in human milk as compared to bovine milk and levels in human colostrum versus normal milk are summarized. The few most widely studied human milk enzymes are discussed in more detail. Evidence is presented to support the views that 1) lipoprotein lipase and ribonuclease are probably spilled into the milk from the blood; 2) lysozyme is spilled from the secretory epithelial cells; 3) lactate and malate dehydrogenases, glucose-6-phosphate dehydrogenase, and lactose synthetase are synthesized in the mammary gland in response to hormonal stimuli; and 4) bile salt stimulated lipase, diastase, protease, and lysozyme are present in sufficient quantities to aid infants in growth and nutrition. Consideration must be given to standardizing the various enzyme assay procedures and activity units so that meaningful comparisons between various studies could be made.

Relation between Dietary Fat, Fat Content of Milk and Concentration of Certain Enzymes in Human Milk

Relation between Dietary Fat, Fat Content of Milk and Concentration of Certain Enzymes in Human Milk

COMMITTEE ON NUTRITION

Treatment of raw cow's milk with pancreatic proteolytic enzymes reduces curd tension to levels comparable to those achieved by many other methods suitable for the preparation of soft-curd milk. No other biologic or nutritional benefits have been shown to result from enzyme treatment of milk. No evidence is available for assigning any benefit in infant nutrition to the proteolytic activity naturally occurring in human milk or persisting in enzyme-treated cow's milk after pasteurization. Argument based on the mere existence of proteolytic enzymes in human milk cannot justify enthusiastic claims for use of enzyme-treated milk in infant feeding. The subject of enzymes in milk and their potential role in infant feeding has received scant attention; further study may reveal information which will call for reappraisal in the future.