The complete cDNA nucleotide sequence of a novel cathepsin derived from mou
se placenta, termed cathepsin P, was determined. mRNA for cathepsin P was e
xpressed in placenta and at lower levels in visceral yolk sac, but could no
t be detected in a range of adult tissues. The expression pattern of this p
rotease indicates that it probably plays an important role during implantat
ion and fetal development.