Recombinant Bombyx mori Membrane alanyl aminopeptidase
Description
Definition and Biological Role
Recombinant Bombyx mori membrane alanyl aminopeptidase (mAAP) refers to the genetically engineered version of the native enzyme, expressed in heterologous systems for detailed characterization. mAAP is a type II integral membrane glycoprotein anchored to the apical brush border membrane of midgut epithelial cells. It catalyzes the removal of N-terminal amino acids from oligopeptides, facilitating nutrient absorption .
Recombinant Expression Systems
Recombinant mAAP is typically produced using:
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Baculovirus/Insect Cell Systems: Preserves native glycosylation patterns and membrane localization .
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Escherichia coli: Used for non-glycosylated forms to study core enzymatic activity .
Purification Methods:
Functional Properties
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Substrate Specificity: Broad activity toward unsubstituted oligopeptides, with preference for alanine residues at the N-terminus .
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Enzymatic Activity: Optimal pH range of 7.0–8.5 and temperature stability up to 40°C .
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Toxin Interaction: Binds Bacillus thuringiensis (Bt) Cry toxins, implicating mAAP as a receptor in toxin-mediated insect lethality .
5.1. Toxin Binding and Insecticidal Resistance
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Cry1Ac and related Bt toxins interact with mAAP on midgut brush border membranes, disrupting epithelial integrity .
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Ligand Binding Assays: Cry toxins show prominent binding to ~110 kDa mAAP isoforms in Bombyx mori .
5.2. Isoform Diversity
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Bombyx mori expresses multiple mAAP isoforms (e.g., APN1, APN4, APN9) with molecular weights ranging from 88–114 kDa .
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Key Isoform Features:
