Ionogenic Groups in the Active Site of Lysostaphin. Kinetic and Thermodynamic Data Compared with X-Ray Crystallographic Data

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V. I. Surovtsev, V. M. Borzenkov, T. V. Fedorov^*, and O. I. Smotrov

State Research Center of Applied Microbiology and Biotechnology, Russian Federation Ministry of Health, 142279 Obolensk, Moscow Region, Russia; fax: (496) 736-0010; E-mail: tfedorov@yandex.ru

^* To whom correspondence should be addressed.

Received May 15, 2007

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The active site of lysostaphin is shown to contain a residue of glutamic acid. As judged by a pK value of 9.2 (with pentaglycine bridges in peptidoglycan of staphylococci as a substrate), another ionogenic residue could be the epsilon-amino group of a lysine. However, the pH value near a negatively charged cell is supposed to be strongly shifted to acidity as compared to the pH of the solution volume. This shifts the enzyme pH dependence curve in solution to alkalinity. Therefore, the other group might be histidine, which is consistent with the X-ray crystallographic data. A similar shift is likely to occur for lysozyme in the case of Micrococcus lysodeikticus cells. Determination of pK of ionogenic groups in the active sites of alkaline enzymes responsible for lysis of negatively charged bacterial cells gives their apparent values because the “pericellular” and “voluminous” values of pH are not coincident.

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KEY WORDS: lysostaphin, lysozyme, staphylococcus, active site, enzymatic catalysis

DOI: 10.1134/S0006297907090106

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