A new metallo- endopeptidase from human neuroblastoma NB-OK-1 cells which inactivates atrial natriuretic peptide by selective cleavage at the Ser123-Phe124 bond

Abstract

A novel metallo-endopeptidase from human neuroblastoma NB-OK-1 cells was partially purified and characterized. This enzyme activity was detected in the culture medium and could be detached from intact cells by gentle washing, suggesting a peripheral localization of the enzyme. This endopeptidase inactivated Atrial Natriuretic Peptide (ANP) by a unique and selective cleavage of the Ser123-Phe124 bond. It also produced hydrolysis at the Xaa-Phe, Xaa-Leu, or Xaa-Ile bonds of other peptide hormones such as bradykinin, somatostatin 14, litorin, substance P, neuromedin C and angiotensin II. The substrate selectivity and inhibition profile of the enzyme showed obvious similarities with the peptide hormone inactivating endopeptidase (PHIE) recently purified from Xenopus laevis skin secretions and indicated a thermolysin-like activity distinct from neutral endopeptidase (EC 3.4.24.11) and from angiotensin converting enzyme (EC 3.4.15.1).

Atrial natriuretic peptide binds to ANP-R1 receptors in neuroblastoma cells or is degraded extracellularly at the Ser-Phe bond

“…Bacitracin is known to prevent unspecifically the breakdown of several peptides. In addition, the dégradation System of NB-OK-1 cells, in its soluble form (that présent in the médium), showed an optimal pH at 7.0 and was partially inhibited by 1,10-phenanthroline and EDTA, suggesting the participation of a neutral metalloproteinase (Delporte et al, 1992).…”

Biochemistry of natriuretic peptides

“…Three enzyme candidates, with similar specificity in cleaving the carboxy-terminal end of ANP, have been found in bovine vascular smooth muscle and endothelial cells [154]. rat brain [155], and neuroblastoma cells, [156] but their importance in ANP metabolism has yet to be determined. The metabolism of BNP and CNP is still being evaluated.…”

Characterization of the thermolysin-like cleavage of biologically active peptides by Xenopus laevis peptide hormone inactivating enzyme

“…For now, it can be envisioned that its affinity and specificity for peptide substrates of higher organisms may indicate that there are closely related endopeptidases present in mammals. Preliminary observations on various human tumor cell lines suggesting the presence of enzymes of similar specificity (Delporte et al, 1992;Carvalho et al, 1993) may further support the idea that, together with PHIE, they may represent specimen of a novel endopeptidase family related to NEP and thermolysin.…”