Human serum was found to contain
enzyme activities hydrolyzing succinyl
trialanine paranitroanilide and 3H-kappa-elastin
Sepharose substrates. Both types of activities could be partly abolished by
serine active site titrants (phenylmethanesulfonylfluoride, diisopropylphosphorofluoridate) and partly by neutral
chelating agents (
EDTA; 1-10-
phenanthroline). The combination of phenylmethanesulfonylfluoride and
EDTA gave a complete inhibition of human serum
elastase-type activities indicating the presence of at least two different types of elastases (
serine and
metalloproteases) in human serum. In nonsmokers, the average serum
elastase-type activity on succinyl
trialanine paranitroanilide was found equal to 78.1 ng/ml porcine
pancreatic elastase equivalents and on 3H-kappa-elastin
sepharose beads equal to 688.8 ng/ml. No statistically significant differences were observed in
elastase levels in the sera of individuals presenting clinical symptoms of
atherosclerosis. The sera of patients suffering from chronic
obstructive lung diseases contained, however, higher amounts of
elastase-type activities, respectively equal to 237.2 ng/ml on succinyl
trialanine paranitroanilide and 1,096 ng/ml on 3H-kappa-elastin
Sepharose beads and was quantitatively significant when compared with control subjects.