Intracellular Peptidoglycan Hydrolases of the Bacterium Xanthomonas campestris XL-1

B. V. Sitkin, I. M. Tsfasman, O. A. Stepnaya^*, and I. S. Kulaev

Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, pr. Nauki 5, Pushchino, Moscow Region 142290, Russia; fax: (095) 956-3370; E-mail: kulaev@ibpm.serpukhov.su

^* To whom correspondence should be addressed.

Received March 15, 2002; Revision received April 22, 2002

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A system of intracellular peptidoglycan hydrolases of Xanthomonas campestris XL-1 comprises about 10 enzymes of different localization and substrate specificity. Seven enzymes (A₁-A₇) are localized in cytosol, one enzyme (A₈) in periplasm, and two enzymes (A₉, A₁₀) were found in the fraction of cell walls and membranes. While the culture is entering the logarithmic growth stage from the stationary stage, a change occurs in the activity of the cytosolic enzymes: A₁ significantly increases, and A₅ and A₆ decrease. The spectrum of cytosolic enzymes also depends on the growth medium composition. The enzyme A₇ present in cells secreting extracellular enzymes (medium 5/5) was not found in non-secreting cells (LB medium). Unlike extracellular enzymes, intracellular peptidoglycan hydrolases are primarily acidic proteins. The data indicate that the system of intracellular peptidoglycan hydrolases of X. campestris is under complex and strict regulation.

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KEY WORDS: intracellular peptidoglycan hydrolases, Xanthomonas campestris, lysis, autolysis

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