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NRD convertase and aminopeptidase B: two processing metallopeptidases with a selectivity for basic residues
1Laboratoire de Biochimie des Signaux Régulateurs Cellulaires et Moléculaires, Université Pierre et Marie-Curie, Paris, France.
Annales D'Endocrinologie
|January 1, 1997
Summary
Two rat testis enzymes, NRD convertase and aminopeptidase B, were characterized. NRD convertase processes specific peptide bonds, while aminopeptidase B removes N-terminal residues, suggesting roles in spermatogenesis.
Area of Science:
- Biochemistry
- Enzymology
- Molecular Biology
Background:
- Rat testis contains various proteases crucial for reproductive functions.
- Understanding specific endoprotease and exopeptidase activities is key to elucidating spermatogenesis mechanisms.
Purpose of the Study:
- To isolate and characterize a metalloendopeptidase and an aminopeptidase B from rat testis.
- To investigate the expression patterns and potential physiological roles of these enzymes during spermatogenesis.
Main Methods:
- Enzyme isolation and purification from rat testis.
- Biochemical assays to determine substrate specificity and kinetic properties.
- Immunochemical studies to assess enzyme distribution and expression levels.
- Sequence homology analysis to classify the identified enzymes.
Main Results:
- A 1161-residue metalloendopeptidase, NRD convertase (EC 3.4.24.61), was identified with a Zn(2+)-binding site and specificity for N-terminal Arg in dibasic sites.
- A 72 kDa metalloexopeptidase, aminopeptidase B, capable of removing Lys and Arg residues, was characterized.
- Both enzymes are highly expressed in late spermatogenesis, with NRD convertase exclusively in germ cells.
- Subcellular localization suggests aminopeptidase B's role in the secretory pathway and raises new hypotheses for NRD convertase.
Conclusions:
- NRD convertase and aminopeptidase B are key enzymes in rat testis, particularly during late spermatogenesis.
- Their distinct substrate specificities and expression patterns suggest specialized roles in germ cell development and function.
- Further research is needed to fully elucidate the physiological functions of NRD convertase in spermatogenesis.