[Proteolytic enzymes bound to Bac. thuringiensis crystals].

Area of Science:

• Biochemistry
• Molecular Biology
• Insect Pathology

Context:

• Crystals of entomopathogenic proteins from Bacillus thuringiensis (Bt) are widely studied for their insecticidal properties.
• Previous research has reported conflicting data regarding the precise composition and degradation of these protein crystals.

Purpose:

• To investigate the presence and nature of proteinase enzymes within Bt crystals.
• To elucidate the role of these enzymes in the degradation of crystal proteins and explain discrepancies in literature data.

Summary:

• Bt crystals harbor proteinase admixtures, either surface-adhered or within lattice defects.
• Proteolytic activity, amplified by crystal dissolution, progressively degrades high-molecular-weight crystal proteins (140,000–129,000 Da) into smaller components.
• Enzymes identified include serine proteases, metalloproteases, and leucine aminopeptidase, with a novel method developed for enzyme separation.

Impact:

• Provides a molecular explanation for variability in reported Bt crystal compositions.
• Enhances understanding of Bt crystal structure, stability, and activation mechanisms.
• Offers insights into the biochemical interactions governing Bt insecticidal activity and potential applications.