Angiotensin I-converting enzyme (ACE) is a type I transmembrane protei
n composed of two domains (N and C domains) which undergoes a post-tra
nslational proteolytic cleavage in mammalian cells to release the solu
ble ectodomain. The protease involved in ACE cleavage-secretion (ACE-s
ecretase) is not well characterised and eludes isolation: the presence
of a yeast homologue, thus more amenable to genetic manipulation, wou
ld facilitate its identification. We have expressed a secreted form of
the ACE C domain; lacking the C-terminal membrane anchor (C domain(De
lta COOH)), and the membrane-anchored C domain (C domain) in the yeast
Pichia pastoris by fusion to prepro-alpha-factor. Immunofluorescent l
abelling localises the ACE C domain to the periphery of yeast cells bu
t not C domain(Delta COOH), however, expression of both C domain and C
domain(Delta COOH) produced soluble enzymes in the culture medium. Im
munocharacterisation of the two soluble forms of the C domain indicate
s a proteolytic cleavage of the membrane-bound C domain to produce the
soluble counterpart. Thus ACE undergoes a proteolytic cleavage in yea
st. (C) 1997 Elsevier Science Ireland Ltd.