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Release and Functional Characterization of the Leukotriene D 4 ‐Metabolizing Enzyme (Dipeptidase) from Human Polymorphonuclear Leucocytes
Author(s) -
RAULF M.,
KÖNIG W.,
KÖLLER M.,
STÜNING M.
Publication year - 1987
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.1365-3083.1987.tb01076.x
Subject(s) - dipeptidase , extracellular , chemistry , calcium , enzyme , leukotriene d4 , biochemistry , incubation , leupeptin , receptor , organic chemistry , antagonist , protease
Polymorphonuclear leucocytes released LTD 4 ‐dipeptidase activity in a time‐, calcium‐, and cell number‐dependent fashion. The LTD 4 ‐dipeptidase released from polymorphonuclear leucocytes (PMN) by incubation with calcium (0.91 m m ) was detectable up to a cell concentration of 1 × 10 6 /ml and increased with higher concentrations. Maximal LTD 4 ‐dipeptidase activity within the extracellular environment was detected after 15 min of incubation (2x10 7 /ml) in the presence of 2–4.5 m m calcium or after 30 min, when stimulation was carried out with 0.91 m m calcium. The activity of the released LTD 4 ‐dipeptidase was modulated by various metal ions and other compounds. The addition of Mn 2+ Co 2+ , and Zn 2+ (final concentration 1 m m ) enhanced the LTD 4 ‐dipeptidase activity, while Cu 2+ led to a complete inhibition. In the absence of exogenoas calcium EDTA inhibited LTD 4 ‐dipeptidase. Calcium up to a concentration of 5 and 10m m decreased the dipeptidase activity. The LTD 4 ‐dipeptidase is not affected by bestatin, leupeptin. or N‐ethyl‐maleinimide (NEM). The K m of LTD 4 ‐dipeptidase for LTD 4 was 0.95±0.2μ m and v max was 737.5±112.5 pmol/min × mg protein (n = 3±SEM). The highest LTD 4 dipeptidase activity was obtained at physiological pH values. LTD 4 ‐dipeptidase activity can also be released from other cell types, but the enzyme activity from human PMN exceeded that of other cells (e.g. human lymphocytes/monocytes and basophils (LMB) and human lung cell suspension).