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Isolation and partial characterization of five myotropic peptides present in head extracts of the cockroach
Abstract:
Five peptides were isolated by reverse-phase HPLC from head extracts of the cockroach Leucophaea maderae. Four of the peptides were inactivated by aminopeptidase M (APM). The inability of APM to digest the fifth peptide suggests a blocked NH2-terminus. Four of the peptides were inactivated by carboxypeptidase Y (CPY). The activity of the fraction which would have contained proctolin was decreased by about 20%. The complete deactivation of proctolin by CPY indicated that a second peptide, co-eluting with proctolin but refractory to CPY digestion, was responsible for 80% of the biological activity in that fraction. Concentrations of the peptides necessary to produce a threshold response from the isolated cockroach hindgut ranged from 0.009 to 0.083 head equivalents/ml.
Insights
Five cockroach peptides were isolated, with four inactivated by enzymes. A fifth peptide, possibly with a blocked N-terminus, and another peptide resistant to digestion, showed significant biological activity in hindgut responses.
Area of Science:
- * Insect neurobiology and peptide biochemistry.
- * Analysis of neuropeptides in invertebrates.
Background:
- * Cockroach head extracts contain biologically active peptides.
- * Understanding peptide function requires enzymatic characterization.
Purpose of the Study:
- * To isolate and characterize peptides from Leucophaea maderae head extracts.
- * To investigate the enzymatic susceptibility of these peptides.
Main Methods:
- * Reverse-phase High-Performance Liquid Chromatography (HPLC) for peptide isolation.
- * Enzymatic digestion assays using aminopeptidase M (APM) and carboxypeptidase Y (CPY).
- * Assessment of biological activity on isolated cockroach hindgut preparations.
Main Results:
- * Five distinct peptides were isolated via HPLC.
- * Four peptides were inactivated by APM, suggesting accessible N-termini.
- * CPY inactivated four peptides, with one co-eluting peptide responsible for 80% of activity in the proctolin fraction, indicating resistance to digestion and a potential blocked N-terminus.
Conclusions:
- * The study identified multiple peptides in cockroach head extracts with varying enzymatic stability.
- * A novel peptide, resistant to CPY, contributes significantly to biological activity previously attributed solely to proctolin.
- * Peptide characterization is crucial for understanding insect neuroendocrine systems.