Synthetic peptide substrates as models to study a pro-ocytocin/neurophysin converting enzyme

Area of Science:

• Biochemistry
• Molecular Biology
• Endocrinology

Background:

• Hormone precursors contain paired basic amino acids that require specific enzymatic processing for maturation.
• The ocytocin/neurophysin precursor's aminoterminal domain is critical for understanding these processing events.

Purpose of the Study:

• To elucidate the selectivity and mechanism of endoprotease cleavage at paired basic amino acids in hormone precursors.
• To investigate the role of specific amino acid sequences and conformations in enzyme recognition.

Main Methods:

• Synthesis of peptide analogues based on the (1-20)-aminoterminal domain of the ocytocin/neurophysin precursor.
• Cleavage assays using an endoprotease purified from bovine pituitary secretory granules.
• Analysis of enzyme activity on substrates with amino acid substitutions around the basic doublet.

Main Results:

• The processing endoprotease strictly requires basic amino acids to be present in tandem (paired).
• Substitutions in or around the basic doublet significantly affected cleavage efficiency.
• A specific conformation of the basic doublet appears to be preferred by the enzyme.

Conclusions:

• The enzyme's strict requirement for tandem basic amino acids is a key feature of hormone precursor processing.
• The identified conformational preference suggests a conserved mechanism in the ocytocin/neurophysin precursor's aminoterminal domain.
• This research provides insights into the molecular basis of neuropeptide processing and maturation.