Primary structure homologies between two zinc metallopeptidases, the neutral endopeptidase 24.11 ("enkephalinase") and thermolysin, through clustering analysis.

Analogies in the sequences of two related zinc metallopeptidases, the bacterial thermolysin (316 amino acids) and the recently cloned neutral endopeptidase 24.11 ("enkephalinase", 749 amino acids), have been demonstrated by a hydrophobic cluster analysis method derived from the Lim theory. Two sequence alignments are proposed for the entire primary structure of thermolysin and the C-terminal part of endopeptidase 24.11. Except for an arginine residue, all the amino acids involved in the active site of thermolysin have been retrieved in both models of endopeptidase 24.11 within conserved clustered structures. The first model is characterized by a deletion of the Ca2+-binding coil present in thermolysin and the second by replacement of this coil by two alpha-helices. In both models an Arg residue can be located in the active site of the neutral endopeptidase.