Polysaccharide Kinase Activity of Human Milk IgG Antibodies

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N. A. Karataeva, V. N. Buneva, and G. A. Nevinsky^*

Institute of Chemical and Fundamental Medicine, Siberian Division of the Russian Academy of Sciences, pr. Akademika Lavrent'eva 8, 630090 Novosibirsk, Russia; fax: (383) 333-3677; E-mail: nevinsky@niboch.nsc.ru

^* To whom correspondence should be addressed.

Received March 6, 2006; Revision received June 16, 2006

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A small fraction of human milk IgG antibodies is shown to possess polysaccharide kinase activity for the first time. Unlike all known kinases, IgG antibodies can use as phosphate donor not only [gamma-³²P]ATP, but also directly [³²P]ortho-phosphate. Human milk IgGs therefore possess high affinity to ortho-phosphate (K_m = 9-71 µM), which is a more effective substrate than ATP. IgG antibodies possessing polysaccharide kinase activity are yet another example of natural abzymes possessing not hydrolytic, but synthetic enzymatic activity.

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KEY WORDS: human milk, catalytically active IgG, phosphorylation of oligo- and polysaccharides

DOI: 10.1134/S000629790611006X

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