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Catalytic antibodies capable of digesting crucial proteins of pathogenic bac-teria have long been sought for potential therapeutic use. Helicobacter pyloriurease plays a crucial role for the survival of this bacterium in the highly acidic conditions of human stomach. The HpU-9 monoclonal anti-body (mAb) raised againstH. pyloriurease recognized thea-subunit of the urease, but only slightly recognized theb-subunit. However, when isolated both the light and the heavy chains of this antibody were mostly bound to the b-subunit | ềFEBS Journal Specific degradation of H. pylori urease by a catalytic antibody light chain Emi Hifumi1 2 Kenji Hatiuchi2 Takuro Okuda2 Akira Nishizono3 Yoshiko Okamura1 2 and Taizo Uda1 2 1 PrefecturalUniversity of Hiroshima Faculty of Bioscience and Environment Hiroshima Japan 2 CREST of JST Japan Science and Technology Corporation Saitama Japan 3 Oita University Faculty of Medicine Oita Japan Keywords catalytic antibody light chain Helicobacter pylori urease proteolysis Correspondence T. Uda Faculty of Bioscience and Environment PrefecturalUniversity of Hiroshima Shobara Hiroshima 727-0023 Japan Fax 81 824 74 0191 Tel 81 824 74 1756 E-mail uda@pu-hiroshima.ac.jp Received 29 April2005 revised 7 July 2005 accepted 18 July 2005 doi 10.1111 j.1742-4658.2005.04869.x Catalytic antibodies capable of digesting crucial proteins of pathogenic bacteria have long been sought for potential therapeutic use. Helicobacter pylori urease plays a crucial role for the survival of this bacterium in the highly acidic conditions of human stomach. The HpU-9 monoclonal antibody mAb raised against H. pylori urease recognized the a-subunit of the urease but only slightly recognized the b-subunit. However when isolated both the light and the heavy chains of this antibody were mostly bound to the b-subunit. The cleavage reaction catalyzed by HpU-9 light chain HpU-9-L followed the Michaelis-Menten equation with a Km of 1.6 X 10 5 M and a kcat of 0.11 min-1 suggesting that the cleavage reaction was enzymatic. In a cleavage test using H. pylori urease HpU-9-L efficiently cleaved the b-subunit but not the a-subunit indicating that the degradation by HpU-9-L had a specificity. The cleaved peptide bonds in the b-subunit were L121-A122 E124-G125 S229-A230 y241-D242 and M262-A263. BSA was hardly cleaved by HpU-9-L again indicating the digestion by HpU-9-L was specific. In summary we succeeded in the preparation of a catalytic antibody light chain capable of specifically digesting the b-subunit of H.
