Human Milk Lipases

Warded, J.M., Wright, A.J., Bardsley, W.G. and D Souza, S.W. (1984) Bile salt-stimulated lipase and esterase activity in human milk after collection, storage, and heating nutritional implications. Pediatr. Res. 18, 382-386. 

Several studies have been conducted on calcium-fat interactions in human infants (64-70). Low synthesis of bile salts and low pancreatic lipase activity may be responsible for poorer fat utilization in infants than in adults (63,71). Fat from infant formulas may be lower than that from human milk because of the lack of a bile-stimulated lipase in the former (72). In infants, fat absorption tends to decrease with increase in fatty acid length, with lower degree of saturation, and with increase of total fat (3). Triglyceride structure may also influence fat absorption in the infant and, thus, indirectly, might also affect calcium absorption in the infant. 

In addition to LPL, human milk contains a bile salts-activated lipase, which probably contributes to the metabolism of lipids by breast-fed babies who have limited pancreatic lipase activity. Bovine milk and milks from other dairy animals do not contain this enzyme. 

Human Milk Lipases. Two lipases have been identified in human milk by Hernell and Olivecrona (1974A,B). One of these, lipoprotein... 

Hall, B., Muller, D. P. R, and Harries, J. T. 1979. Studies of lipase activity in human milk. Proc. Nutr. Soc, 38, 114A. 

Hyasawa, H., Kiyosawa, I. and Nagasawa, T. 1974. Some observations on human milk lipase. Proc. XIXth Int. Dairy Congr. IE, 559. 

Hernell, O. 1975. Human milk lipases. III. Physiological implications of the bile-salt stimulated lipase. Eur. J. Clin. Invest. 5, 267. 

Hernell, O. and Olivecrona, T. 1974A. Human milk lipases. I. Serum-stimulated lipase. J. Lipid Res. 15, 367-374. 

Wang, C. S. 1981. Human milk bile salt-activated lipase. J. Biol. Chem. 256, 10198-10203. 

Bemback, L fiiacabcig, and G. Hcmcli. The compieie digestion of human milk triacylglyccxol In vitro requires gastric lipase, pancreatic colipase-depcndent lipase and bile salt-stimulated lipase. J. Clio. Invest. Jf5 1221 (1990). 

L. Biadcbeig, O. Hemell, and T. Olivecrona. Hydrolysis of human milk fit globules by pancreatic lipase 7. Ctin, Invest. 67 1741 (I9BIX... 

Bernback, S., Blackberg, L., Hernell, O. 1989. The complete digestion of human milk triacyl-glycerol in vitro requires gastric lipase, pancreatic colipase-dependent lipase, and bile salt-stimulated lipase.. / Clin. Invest. 85, 1221-1226. 

Christie, W.W. 1994. Composition and structure of milk lipids. In Advanced Dairy Chemistry Vol. 2, Lipids, 2nd edn. (P.F. Fox, ed.), Chapman and Hall, London, pp. 1-36. Christensen, T.C., Holmer, G. 1993. Lipase catalyzed acyl-exchange reactions of butteroil, synthesis of a human milk fat substitute for infant formulas. Milchwissenschaft 48, 543-548. 

Human milk differs from cows milk in that it contains two lipases, a lipoprotein lipase and a bile salt-stimulated lipase. The ability of the latter to cause considerable hydrolysis of ingested milk lipids has important nutritional implications. 

There were several new developments during the 1970s. Of particular importance was the purification and characterization of a lipoprotein lipase (LPL) and the acceptance of the postulate that this was the major, if not the only, lipase in cows milk (Olivecrona, 1980). Similarly, the elucidation of the lipase system in human milk as consisting of an LPL and a bile salt-stimulated lipase, and the possible role of the latter in infant nutrition, were noteworthy (Fredrikzon et al, 1978). Also, microbial lipolysis assumed substantial significance with the widespread use of low-temperature storage of raw milk and the recognition that heat-stable lipases produced by psychrotrophic bacteria were a major cause of flavor problems in stored dairy products (Law, 1979). 

Human milk differs from cows milk in that it contains, in addition to an LPL similar to that in cows milk, a bile salt-stimulated lipase (BSSL), which appears to have no counterpart in cows milk (Hernell and Blackberg, 1994). In addition, a third lipase known as platelet-activating factor acet-ylhydrolase activity (PAF-AH) has been demonstrated in human milk the activity is absent, or extremely low in cows milk (Furukawa, et al., 1994). 

Human milk is unusual in containing a lipase that is activated by bile salts. BSSL has been found in the milk of only a few other mammals gorilla (Freudenberg, 1966), cat, and dog, (Freed et al., 1986), and ferret (Ellis and Hamosh, 1992). Ferret milk contains up to 20 times as much BSSL as human milk and constitutes a significant proportion (1-2%) of the total milk protein. BSSL in human milk is present in multimolecular forms, which differ from each other by the extent or quantity of glycosylation in the proline-rich region of the C-terminus of the enzyme (McKillop et al., 2004). 

Carboxylesterase activity is elevated in mastitic milk and colostrum (Fitz-Gerald et al., 1981) and may correspond to that of the reported lipases from somatic cells (Gaffney and Harper, 1965 Azzara and Dimick, 1985a) and colostrum (Driessen, 1976), respectively. The retinyl esterase activity that co-purifies with, but can be separated from, LPL may also be due to a carboxylesterase (Goldberg et al., 1986). It is of interest that the BSSL in human milk that has been shown to be identical with pancreatic carboxylesterase, has retinyl esterase activity (O Connor and Cleverly, 1989). 

Cows milk LPL has phospholipase Ai activity (Scow and Egelrud, 1976), but its action on milk phospholipids has not been recorded. Freshly secreted goats milk has been shown to have phospholipase A activity (Long and Patton, 1978) but it is not known whether this can be attributed to the LPL of that milk. Human milk contains an acid sphingomylinase C, as well as ceramidase activity provided by the bile salt-stimulated lipase present (Nyberg et al., 1998). 

Berkow, S.E., Freed, L.M., Hamosh, M., Bitman, J., Wood, D.L., Elapp, B., Elamosh, P. 1984. Lipases and lipids in human milk effect of freeze-thawing and storage. Pediatr. Res. 18, 1257-1262. 

Blackberg, L., Angquist, K.A., Hernell, O. 1987. Bile salt-stimulated lipase in human milk evidence for its synthesis in the lactating mammary gland. FEBS Letts 217, 37 11. 

Blackberg, L, Hernell, O., Olivecrona, T. 1981a. Hydrolysis of human milk fat globules by pancreatic lipase. J. Clin. Invest. 67, 1748-1752. 

Castberg, H.B., Hernell, O. 1975. Role of serum-stimulated lipase in lipolysis in human milk. 

Freed, L.M., York, C.M., Hamosh, P., Mehta, N.R., Hamosh, M. 1987. Bile salt-stimulated lipase of human milk characteristics of the enzyme in the milk of mothers of premature and full-term infants. J. Pediat. Gastroenterol. Nutr. 6, 598-604. 

Hernell, O. 1985. Specificity of human milk bile salt-stimulated lipase. J. Pediatr. Gastroenterol. Nutr. 4, 517-519. 

Hernell, O., Blackberg, L. 1994. Human milk bile salt-stimulated lipase functional and molecular aspects. J. Pediatr. 125 (Suppl. 2), S56-S61. 

McKillop, A M., O Hare, M.M.T., Craig, J.S., Halliday, H.L. 2004. Characterization of the C-terminal region of molecular forms of human milk bile salt-stimulated lipase. Acta Paediatr. 93, 10-16. 

Neville, M.C., Waxman, L.J., Jensen, D., Eckel, R.H. 1991. Lipoprotein lipase in human milk compartmentalization and effect of fasting, insulin and glucose. J. Lipid Res. 32, 251-257. 

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