ABSTRACT
Two soluble post-proline cleaving peptidase activities, PPCP1 and PPCP2, were demonstrated in Tenebrio molitor larval midgut with the substrate benzyloxycarbonyl-L-alanyl-L-proline p-nitroanilide. Both activities were serine peptidases. PPCP1 was active in acidic buffers, with maximum activity at pH 5.3, and was located mainly in the more acidic anterior midgut lumen. The dynamics of PPCP1 activity and the total activity of soluble digestive peptidases in the course of food digestion were similar, suggesting that the enzyme participates in protein digestion. PPCP2 is a nondigestive soluble tissue enzyme evenly distributed along the midgut. An increase in the activity of PPCP2 was observed in buffers of pH 5.6-8.6 and was maximal at pH 7.4. The sensitivity of PPCP2 to inhibitors and the effect of pH are similar to prolyl oligopeptidases with a cysteine residue near the substrate binding site.
Subject(s)
Insect Proteins/analysis , Peptide Hydrolases/analysis , Proline/metabolism , Tenebrio/enzymology , Animals , Digestive System/enzymology , Hydrogen-Ion Concentration , Insect Proteins/metabolism , Larva/enzymology , Peptide Hydrolases/metabolism , Tenebrio/growth & developmentABSTRACT
Proteins of parasporal crystals (Cry proteins) from entomopathogenic bacterium Bacillus thuringiensis (subspecies kurstaki, galleriae, tenebrionis) as well as some fragments of these proteins, obtained by limited proteolysis, are capable of antimicrobial action against anaerobic bacteria and archaea-Clostridium butyricum, Clostridium acetobutylicum and Methanosarcina barkeri. The MICs are 45-150 microg/mL. Electron microscopy showed that lysis of M. barkeri cells in the presence of 49kDa fragment of Cry3Aa toxin is generally similar to the bacterial cell lysis, which has been previously detected in the presence of Cry11A, Cry1Ab and other Cry proteins. The Cry1D-like toxin from crystals of B. thuringiensis subsp. galleriae has been put forward as an example of the supposition that cell wall and some of its components like teichoic acid and N-acetylgalactosamine have possible influence on Cry toxins, enhancing their antimicrobial activity. The possible ecological role of the antimicrobial activity of Cry proteins is also discussed.
Subject(s)
Archaea/drug effects , Bacillus thuringiensis/chemistry , Bacterial Proteins/pharmacology , Bacterial Toxins/pharmacology , Clostridium/drug effects , Endotoxins/pharmacology , Hemolysin Proteins/pharmacology , Peptide Fragments/pharmacology , Bacillus thuringiensis/metabolism , Bacillus thuringiensis Toxins , Bacterial Proteins/chemistry , Bacterial Proteins/isolation & purification , Bacterial Toxins/chemistry , Bacterial Toxins/isolation & purification , Electrophoresis, Polyacrylamide Gel/methods , Endotoxins/chemistry , Endotoxins/isolation & purification , Hemolysin Proteins/chemistry , Hemolysin Proteins/isolation & purification , Microbial Sensitivity Tests , Peptide Fragments/chemistryABSTRACT
Proteins with molecular masses of 36 and 34 kDa (Bti36 and Bti34) were isolated from entomocidal crystals formed by Bacillus thuringiensis ssp. israelensis cells. The samples of Bti36 contained the admixture of a protein with a molecular mass of 33 kDa (Bti33), apparently a product of proteolysis of Bti36. These 3 proteins are significantly different in N-terminal sequences from known delta-endotoxins of B. thuringiensis and show antibacterial activity toward Micrococcus luteus. The combination of Bti36 and Bti33 also suppresses the growth of some other microorganisms including Streptomyces chrysomallus. The effects of the mixture of Bti36 and Bti33 on the M. luteus cell surface and on the surface of S. chrysomallus cells and exospores are similar, but they are different from the effect of endotoxin Cry11A on micrococcal cells.
Subject(s)
Anti-Bacterial Agents/pharmacology , Bacillus thuringiensis/metabolism , Bacterial Proteins/isolation & purification , Bacterial Toxins/chemistry , Endotoxins/chemistry , Micrococcus luteus/drug effects , Streptomyces/drug effects , Aedes/drug effects , Animals , Anti-Bacterial Agents/chemistry , Bacillus thuringiensis/physiology , Bacillus thuringiensis Toxins , Bacterial Proteins/chemistry , Bacterial Proteins/pharmacology , Hemolysin Proteins , Microbial Sensitivity Tests , Micrococcus luteus/ultrastructure , Microscopy, Electron, Scanning , Spores, Bacterial/physiology , Spores, Bacterial/ultrastructure , Streptomyces/ultrastructureABSTRACT
Mosquitocidal endotoxins Cry4B, Cry11A, and CytA from Bacillus thuringiensis ssp. israelensis as well as the products of their limited proteolysis display antibacterial activity relative to Micrococcus luteus. The endotoxin Cry11A also induces the lysis of the micrococcus protoplasts. Potassium and sodium ions and N-acetylgalactosamine increased the antibacterial effect of Cry11A, whereas glucose and N-acetylglucosamine inhibited it. The endotoxin Cry11A displays the antibacterial effect on some other microorganisms.
