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Specificity of the surface aminopeptidase in Moniliformis moniliformis (Acanthocephala)
Abstract:
The hydrolysis of various oligopeptides in solution by intact Moniliformis moniliformis was examined using paper chromatographic analysis of the incubation medium. In the presence of transport inhibitors, the respective peptide sub-units and/or amino acid residues accumulated in the bathing medium. Only peptides with serine, methionine, leucine or alanine at the NH2-terminal end of the peptide were hydrolysed. There was no hydrolysis when these amino acids were located internally or at the COOH-terminus indicating genuine aminopeptidase activity of the class, alpha-aminoacylpeptide hydrolase. Hydrolysis was negligible when the NH2-terminus was arginine, aspartic acid, glutamic acid, glycine, histidine, lysine, phenylalanine, proline, tryptophan, tyrosine, or valine. In separate experiments, mediated uptake of 0.1 mM 3H-leucine by the worms in 2 min was inhibited 100% by 5 mM unlabelled leucine or tri-serine, but only partially inhibited by 5 mM Ser-Gly (66%), 10 mM Ser-Gly (74%), 5 mM Leu-Leu (69%), 10 mM Leu-Leu (70%), 5 mM Leu-Gly (58%) or 5 mM Met-Met (69%). Because the inhibitions produced by 5 mM Leu-Leu plus 5 mM Met-Met (79%) or 5 mM Leu-Leu plus 5 mM Ser-Gly (76%) were not additive, a single enzyme is indicated. The name serine aminopeptidase is proposed because of its preference for serine.
Insights
Moniliformis moniliformis exhibits specific aminopeptidase activity, primarily hydrolyzing peptides with serine at the N-terminus. This suggests a single enzyme, likely serine aminopeptidase, is responsible for this peptide hydrolysis.
Area of Science:
- Biochemistry
- Parasitology
- Enzymology
Background:
- Moniliformis moniliformis is an acanthocephalan parasite.
- Understanding its digestive enzymes is crucial for host-parasite interactions.
Purpose of the Study:
- To investigate the peptide hydrolysis activity of Moniliformis moniliformis.
- To characterize the substrate specificity and identify the enzyme responsible for hydrolysis.
Main Methods:
- Paper chromatographic analysis of incubation media.
- Use of transport inhibitors to study peptide uptake.
- Enzyme inhibition assays with various peptides and amino acids.
Main Results:
- Hydrolysis occurred only for peptides with N-terminal serine, methionine, leucine, or alanine.
- Activity was confirmed as alpha-aminoacylpeptide hydrolase (aminopeptidase).
- Non-additive inhibition patterns indicated a single enzyme, likely serine aminopeptidase, due to its preference for serine.
Conclusions:
- Moniliformis moniliformis possesses a specific aminopeptidase.
- The enzyme shows a preference for serine at the N-terminus.
- This finding contributes to understanding parasite nutrition and metabolism.