Transferrin human milk

The recombinant whole molecules are both expressed in glycosylated form, although the glycosylation patterns differ from the proteins isolated from natural sources. The recombinant human transferrin binds to receptors both in its glycosylated form and as a nonglycosylated mutant, showing that the carbohydrate is not required for receptor binding (230). Recombinant human lactoferrin shows identical spectroscopic properties and shows an identical profile of pH-dependent iron release when compared with human milk lactoferrin (231). 

Lactoferrin was first identified as a red protein fraction in human milk (1). The milk protein has been called by various names of red milk protein, ekkrino-siderophilin, and lactotransferrin which is in turn very similar in many respects to transferrin, the ironbinding protein of serum. The concentration of lactoferrin in human milk is unusally rich with a range of 7 mg/ml in colostrum to approximately 1 mg/ml in mature milk (2). However, the bovine colostrum contains lactoferrin at concentrations of 5 mg/ml, which drops very rapidly with stage of lactation to where mature bovine milk contains 20-200 pg/ml of lactroferrin (3). Lactoferrin is also found in various other exocrine secretions of the body such as vaginal, nasal, bronchial and intestinal (4 6). 

Lactoferrin is an iron transport non-heme glycoprotein present in human milk and many biological secretions that can effectively inhibit the oxidation of various lipid systems by its iron-binding capacity. However, this protein can also have prooxidant activity, depending on the lipid system, and its concentration relative to the concentration of metal ions. Lactoferrin effectively inhibited oxidation and increased the oxidative stability of infant formulas supplemented with iron (see Chapter ll.C). Other known proteins that chelate or inactivate transition metals are found in biological systems including transferrin, albumin, and ceruloplasmin (Chapter 13). 

The antimicrobial properties of the transferrins can be either enhanced or inhibited by a number of substance, especially by components of the very same biological fluids in which the transferrins are found. Many such effects can be demonstrated only in artificially-prepared media. Thus lactoferrin by itself has an antimicrobial effect lower than that observed in the human milk. 

Milk transferrin (lactoferrin51a b c also found in leukocytes), hen egg transferrin (ovotransferrin),52 52a and rabbit and human serum transferrin54 543 all have similar structures. Each Fe3+ is bonded to oxygen anions from two tyrosine side chains, an aspartate carboxy-late, an imidazole group, and the bound carbonate ion (Fig. 16-2B). 

Van Cott K, Lubon H, Gwazdauskas F, et al. Recombinant human protein C expression in the milk of transgenic pigs and the effect on endogenous milk immunoglobulin and transferrin levels. Transgenic Res., 2001 10(1) 43-51. 

The transferrins are glycoproteins (i.e. compounds of proteins and carbohydrates) and include serum transferrin, lactoferrin (present in milk) and ovotransferrin (present in egg white). In humans, serum transferrin transports 40 mg of iron per day to the bone marrow. It contains a single polypeptide chain (molecular weight of 80000) coiled in such a way as... 

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