Lactoperoxidase molecular weight

Lactoperoxidase is associated with the serum proteins of milk. It has an optimum pH of 6.8 and a molecular weight of 82,000. 

We have employed a variety of procedures for removing free iodide from the iodinated proteins. This can be accomplished by (a) gel filtration, (b) dialysis, and (c) use of ion exchange resin. Gel filtration is a very effective method for removal of both iodide and lactoperoxidase if the molecular weight of the iodinated protein and the molecular weight of the enzyme are sufficiently different as in the example given. Since the iodine derivatives are light sensitive all procedures should be carried out in dim light. 

In search of alternatives to Chloramine-T, Morrison (1980) demonstrated that lactoperoxidase from bovine milk was particularly effective for iodide oxidation and the radioiodination of proteins. The single strand polypeptide lactoperoxidase has a molecular weight of approximately 78 kD. The structure of lactoperoxidase contains a prosthetic heme group which is covalently linked to the protein at the active site of the enzyme. In the presence of minute quantities of hydrogen peroxide, lactoperoxidase oxidizes and binds radioiodide to proteins in the reaction mixture. The pH optimum of iodide oxidation by lactoperoxidase is 4-8.5 with an optimum at pH 5. The reaction is extremely rapid, allowing reaction times of less than 1 min. This provides very mild conditions and denaturation of proteins is low. Yields of up to 85% can be obtained and the method is widely used for labeling proteins and hormones. Lactoperoxidase may itself... 

Hemoproteins with One or Several Heme Groups per Molecule. Hemoglobins and catalases contain four atoms of iron per molecule, while cytochrome c and the peroxidases (horse-radish and the lactoperoxidases the molecular weight of the others has not yet been determined) contain one iron atom per molecule. For hemoglobin, this means that the hemes within the same molecule exercise considerable interaction, which is of essential importance for the function of hemoglobin. Whether this is also the case in the catalases is not known. In hemoproteins with one iron atom per molecule (peroxidases and cytochrome c) it is evident that no intra-... 

Horse-radish peroxidase consists of one molecule of ferriprotoporphyrin linked to a colorless protein. The molecular weight is 44,100 (74). Lactoperoxidase contains one molecule per molecule of a greenish ferriporphyrin of unknown composition the molecular weight is 93,000 (85). 

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