Substrate specificity and some physicochemical properties of autolytic enzymes of the bacterium Lysobacter sp. XL 1.

The substrate specificity of autolytic enzymes of the bacterium Lysobacter sp. XL 1 has been established. The periplasmic enzyme A8, the cytosolic enzyme A1, and the enzyme A10 solubilized from the cell walls and membranes with Triton X-100 exhibit glucosaminidase activity; the cytosolic enzyme A4 and the enzyme A9 solubilized from the cell walls and membranes with LiCl exhibit the muramidase activity. The cytosolic enzymes A3 and A6 have N-acetylmuramoyl-L-alanine amidase activity, and the enzyme A5 exhibits the diaminopimelinoyl-alanine endopeptidase activity. Some physicochemical properties of the most active autolytic cytosolic enzymes of Lysobacter sp. XL 1 (endopeptidases A5 and A7 and N-acetylmuramoyl-L-alanine amidase A6) were studied. The enzymes exhibit maximal activity over a wide range of buffer concentrations in weakly alkaline medium and moderate temperatures. The investigated enzymes are comparatively thermolabile proteins.

Intracellular peptidoglycan hydrolases of the bacterium Xanthomonas campestris XL-1.

A system of intracellular peptidoglycan hydrolases of Xanthomonas campestris XL-1 comprises about 10 enzymes of different localization and substrate specificity. Seven enzymes (A(1)-A(7)) are localized in cytosol, one enzyme (A(8)) in periplasm, and two enzymes (A(9), A(10)) 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: A(1) significantly increases, and A(5) and A(6) decrease. The spectrum of cytosolic enzymes also depends on the growth medium composition. The enzyme A(7) 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.

Isolation and properties of peroxidase produced by the fungus Panus tigrinus.

Synthesis of peroxidase and laccase by the fungus Panus tigrinus was significantly stimulated by addition of the lignocellulose substrate to the culture media. Peroxidase was isolated from the culture liquid and some properties of the enzyme were investigated. P. tigrinus peroxidase belongs to a group of extracellular peroxidases similar to the plant type peroxidases.