Changes in Antioxidative Properties of Lactoferrin from Women's Milk during Deamidation

S. Belizy, I. N. Nasarova, V. N. Procof'ev, I. A. Sorokina^*, N. V. Puschkina, and A. I. Lukach

Department of Biochemistry and Microbiology, School of Biology, Rostov-on-Don State University, Bolshaya Sadovaya ul. 105, Rostov-on-Don, 344006 Russia; fax: (8632) 64-5255; E-mail: bio@rnd.runnet.ru

^* To whom correspondence should be addressed.

Received October 2, 2000; Revision received January 9, 2001

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Spontaneous deamidation of lactoferrin preparations from women's milk was found during incubation for 28 days under simulated physiological conditions (0.85% NaCl, pH 7.0, 37°C). After 28 days of incubation, this deamidation was associated with a 12% decrease in the total amide content in the protein. Addition of deamidated preparation to a suspension of lipoproteins from egg yolk in the presence of Rhodamine 6G decreased the total intensity of rapid and slow emission and also the intensity of the slow emission of Fe²⁺-induced chemiluminescence by 37, 48, and 53%, respectively, suggesting an increase in the antioxidative activity of lactoferrin during deamidation. Deamidation obviously stimulated the nonspecific interaction of lactoferrin with iron ions and, consequently, increased the antioxidant effect of the protein in this way. This was supported by the finding of decreased antioxidative effectiveness of lactoferrin during its complete saturation with iron under the incubation conditions.

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KEY WORDS: lactoferrin, deamidation, chemiluminescence, free radical reactions

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