Casein iodination

Serum albumin labeled with an iodine radionuclide was firstly used as a substrate for determining protease activity by Absolon This method was later on modified several times and applied for assaying various proteolytic activities in different materials. Mego et al. injected denaturated I-human %rum albumin into the tail vein of rats and measured the rate of intralysosomal proteolysis on isolated lysosomes containing endocytosed substrate. This method was also used for the determining the intralysosomal pH on the basis of differences found in the rate of I-albumin breakdown in intact and lysed lysosomes C-bovine serum albumin, I-casein or I-albumin have been alternatively used as substrate for measuring the activity of trypsin, chymotrypsin and papain - ). 

P8. Pfander, W. H., The effects of iodinated casein, thiouracil and cortisone on the ascorbic acid requirement of the male guinea pig. /. Nutrition 47, 487-501 (1952). 

Groppel etal. (1986) found that the mating frequency of goats and sheep fed casein, starch and cellulose diets without additional iodine was similar to that of animals given supplemental iodine (0.4mg.iodine/kg.diet). However, the dietary iodine deficit increased the abortion rate. As with hypothyroid sows, the gestation period was prolonged and the live-born goitrous kids were less viable than controls. 

Iodine feed supplements must be stable to meet the needs of several groups of farm animals. lodates [Ca(I03)2 X 6H2O Ca(I03)2] and iodides [Nal KI] are both approved feed supplements in the EU (2003, 2005). lodates are more stable than iodides as feed additives and so are used preferentially. Cheeke (1991) suggests that eth-ylenediamine dihydroiodide (EDDI) and pentacalcium orthoperiodate may be suitable feed iodine additives, but does not include information on their stability. In our studies we found that a casein-bound iodine supplement produced by milling casein with KI was highly stable Schone et al., 1997c). 

L-Alanine Bis (aminopropyl) piperazine Carotene Casein Cholecalciferol Choline bitartrate Chondroitin sulfate Copper Copper iodide (ous) Corn (Zea mays) oil Corn (Zea mays) starch L-Cysteine Ferric ammonium EDTA Ferric chloride Ferric chloride hexahydrate 3-Glucan Hesperidin Hydrogenated cottonseed oil L-Hydroxyproline Iodine DL-Leucine Magnesium aspartate Magnesium citrate dibasic Manganese chloride (ous), anhydrous MSG... 

In hydrolysates of iodinated casein, an excess of 3,5-diiodotyro-sine is present in addition to thyroxine. The procedure for the determination of thyroxine is ... 

Essential trace elements with their functions in enzymes and hormones are distributed in different parts of the body. Iodine is special. Some 75% of the total iodine content in the human body (about 14 mg) is found in the thyroid gland, a small organ in the neck. There, it participates in the formation of the important thyroid hormone, thyroxine. This is vital for normal mental and physical development and for regulating the body s metabolism. A recommended daily intake is 100-200 pg. Deficiency of iodine will cause goitre. This has to be treated by additional potassium iodide or iodine casein. In developed countries, iodine deficiencies are now rare because iodine is added to table salt. 

Although earlier workers iodinated proteins, Ostwald in 1910 provided the first unequivocal proof that tyrosine in proteins was iodinated. He isolated diiodotyrosine from iodinated albumin (273), gliadin (274), and casein (275)-. Since then papers on serum albumin, egg albunun, and serum globulin (276), pepsin (6, 7), insulin (125), and the lactogenic hormone (277) all indicate that the action of iodine on these proteins in neutral or slightly alkaline solution is one of substitution on the tyrosine residues. The reaction is as follows ... 

Interesting results were obtained by Ludwig and Mutzenbecher (293) who isolated thyroxine and mono iodotyrotine from iodinated casein. This isolation of thyroxine has bem confirmed (294) and althou the mechanism of its formation is still imcertun most workers are agreed that iodination of tyrosine is one of the first steps (295, 296). 

The different iodine contents of milk albumin on the first day of lactation and of the mature casein milk of goats... 

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