IRCM-Serine Protease 1 (IRCM-SP1) has recently been isolated and characterized from porcine pituitary anterior and neurointermediate lobes (Cromlish et al., 1986a, J. Biol. Chem.261:10850–10858; Cromlish et al., 1986b, J. Biol. Chem.261:10859–10870). This pituitary serine protease was shown to selectively cleave human proopiomelanocortin (POMC)-derived peptides at both pairs of basic residues and C-terminal to specific Arg residues, all known to be cleaved in vivo. Here, a similar enzyme was isolated from rat heart atria and ventricles. Rat IRCM-SP1 was shown to be highly specific for the same cleavage sites in POMC, as the porcine pituitary homologue. Furthermore, the rat and the porcine enzymes cleave rat pro-Atrial Natriuretic Factor (pro-ANF 1–126) to yield ANF 103–126, 102–126 and 99–126 in that order of preference. This suggests that in vitro the cleavage sites preferred in pro-ANF resemble those found in brain and hypothalamus. The enzyme is nine times more abundant in atria versus ventricles/mg protein. It is concluded that IRCM-SP1, could well represent a common pro-hormone maturation enzyme for POMC and Pro-ANF and possibly many other pro-hormones.
Homologous IRCM-Serine Protease 1 from pituitary, heart atrium and ventricle: A common pro-hormone maturation enzyme?
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Nabil G. Seidah, James A. Cromlish, Josée Hamelin, Gaétan Thibault, Michel Chrétien; Homologous IRCM-Serine Protease 1 from pituitary, heart atrium and ventricle: A common pro-hormone maturation enzyme?. Biosci Rep 1 September 1986; 6 (9): 835–844. doi: https://doi.org/10.1007/BF01117107
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