|
|
|
|
Infective larvae of Strongyloides papillosus, freshly isolated
from faeces of experimentally infected rabbits, secreted a collagenolytic
metalloproteinase from their oesophageal glands. The enzyme hydrolyzed
azocoll at the optimal pH of 8.4 and exhibited a very low activity towards
azocasein and azoalbumin at the optimal pH 6.0 and 8.0, respectively. No
degradation of elastin-orcein and keratin-azure was observed at the pH
range of 7.2-10.0.
Under histochemical conditions the proteinase hydrolyzed
N-acetyl-L-methionine-1-naphthylester at
optimal pH 6.8,
whereas other synthetic, N-blocked aminoacyl or peptidyl substrates
bearing such P1 amino acids as L-Ala, L-Phe, L-Arg,
L-Leu, and L-Lys, were
not hydrolyzed. The enzyme was sensitive to refrigeration and underwent
inactivation during lyophilization.
Unlike most proteinases of other families, the metalloenzyme secreted by
S. papillosus larvae was relatively resistant to the
inhibitory action of inorganic zinc salts, the decline in the activity in
the presence of 1 mM ZnSO4 was as low as 20%. The organic mercurial
pHMB,
the nonionic detergent Triton X-100, and calcium ions enhanced the
proteinase activity, whereas the cationic detergent cetyltrimethylammonium
bromide, the anionic detergent SDS, and the thiol compound
dithioerythritol were mild inhibitors. Zinc-chelating compounds
1,10-phenanthroline, N-blocked-L-Pro-L-Leu-Gly hydroxamate,
N-blocked
L-Pro-L-Leu-L-Ala hydroxamate, and
N-carboxymethyl-L-Phe-L-Leu
were strong
inhibitors, whereas specific inhibitors of serine, cysteine and aspartyl
proteinases were without effect on the activity of the larval proteinase.
The secretion expelled from the mouth of the larvae avidly absorbed
the cationic dye toluidine blue (0.001%) at pH 5.5 and the resulting black
complex was water insoluble, thus indicating the presence of a strongly
anionic glycoprotein in the secretion, if not an acid glycoprotein nature of
the proteinase.