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Substrate Specificity of the Human Lymphokine Leucocyte Migration‐Inhibitory Factor (LIF): Radioenzymic Assay and Inhibition by cGMP
Author(s) -
BENDTZEN K.
Publication year - 1979
Publication title -
scandinavian journal of immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.934
H-Index - 88
eISSN - 1365-3083
pISSN - 0300-9475
DOI - 10.1111/j.1365-3083.1979.tb01335.x
Subject(s) - pmsf , lymphokine , chemistry , substrate (aquarium) , trypsin , tosyl , biochemistry , plasmin , enzyme , oligopeptide , leupeptin , in vitro , protease , stereochemistry , biology , peptide , ecology
The human lymphokine, leucocyte migration‐inhibitory factor (LIF), appears to be a serine esterase and protease by virtue of its susceptibility to the irreversible enzyme inhibitor, phenylmethylsulfonyl fluoride (PMSF), and by the ability of arginine esters and amides to protect LIF against PMSF‐induced inactivation. In this paper, three methods are described by which putative substrates for LIF : may be investigated. Thus, molecules satisfying the substrate specificities of this lymphokine should (1) protect LIF against inactivation by PMSK. (2) reduce LIF activity in vitro on polymorphonuclear leucocytes, and (3) reduce the esterolytic activity of purified LIF‐rich supernatants. The first two reactions were tested hy means of the leucocyte migration agarose technique; the third reaction was tested by a sensitive enzyme assay using tritiated tosyl arginine methyl ester as substrate. Guanosine 3′,5’‐cyclic monophosphoric acid, which is capable of protecting LIF against PMSF‐induced inhibition, also inhibitied the esterolytic activity of the purified LIF preparation. Four synthetic oligopeptide substrates for trypsin, thombin and plasmin were investigated. Only one, the thrombin‐ and trypsin‐specific benzoyl‐phenylalanyl‐valyl‐arginie‐ p ‐nitroanilide, possessed high affinity for the LIF molecule and may therefore prove to be a potent substrate for this lymphokine.