Am. J. Respir. Crit. Care Med., Vol 152, No. 2, Aug 1995, 760-764.
Carboxypeptidase M activity is increased in bronchoalveolar lavage in human lung disease
T Dragovic, DE Schraufnagel, RP Becker, M Sekosan, EG Votta-Velis and EG Erdos
Department of Pharmacology, University of Illinois College of Medicine, Chicago, USA.
Carboxypeptidase M (CPM) cleaves the C-terminal arginine and lysine of
peptides; it is expressed in the lung, especially on the plasma membrane of
alveolar type I cells. Here, we report on CPM in human bronchoalveolar
lavage (BAL) collected from 69 patients and analyzed for activity, cell
number and type, and protein level. Seventy-six percent of CPM activity,
measured at pH 7.5 with 5-dimethylamino-
naphthalene-1-sulfonyl-alanyl-arginine (Dansyl-Ala-Arg) substrate, was
immunoprecipitated with polyclonal antibody to purified human enzyme. In
patients without active lung disease, CPM activity in BAL was 7.69 (+/-
2.12) nmol/h/mg protein, but in patients with acute pneumonia, it was 29.25
(+/- 4.06) (p < 0.01). In patients with Pneumocystis carinii pneumonia,
CPM activity was elevated to 26.00 (+/- 4.85) (p < 0.01) and in patients
with lung cancer, to 30.95 (+/- 4.12) (p < 0.01). The activity was not
associated with the cellular elements of BAL. The highest specific activity
was in the large aggregate fraction of surfactant, which also contained the
highest concentration of phosphorus. Transmission electron microscopy of
this fraction revealed the presence of typical lamellar bodies and tubular
myelin structures. The high CPM activity may stem from its induction and
release in acute lung disease. In addition, CPM may be a marker of
infection with certain pathogens and an indicator of type I cell injury in
parenchymal lung diseases.
