Document Detail

Modulation of the 5-lipoxygenase activity of MC-9 mast cells: activation by hydroperoxides.
MedLine Citation:
PMID:  3099336     Owner:  NLM     Status:  MEDLINE    
In order to identify regulatory steps in leukotriene synthesis, the biochemical characteristics of a 5-lipoxygenase activity in the 100,000 xg supernatant from sonicates of cells of an IL-3 dependent murine mast cell clone, MC-9 were determined. Principal products from exogenous 14C-arachidonic acid were identified as leukotriene B4, diastereomeric 5,12-dihydroxy-eicosatetraenoic acids (5,12 diHETEs) 5-hydroperoxy and hydroxyeicosatetraenoic acids (5-HPETE and 5-HETE) as well as a novel metabolite 5-oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE). The crude lipoxygenase activity had a pH optimum of 6.9 and was highly dependent upon added Ca++. The effective Ca++ concentration for 50 per cent activation (EC50) was 3 microM. Activity was also stimulated by ATP (EC50 = 160 microM). The cytosolic 5-lipoxygenase activity exhibited a biphasic concentration dependence for arachidonic acid with maximum product formation occurring at 35 microM (ca. 20 nmole/mg/4 min). The lipoxygenase activity exhibited apparent lag phase kinetics which were more pronounced at low protein concentrations (0.3 mg/ml). In addition, the lag phase was greatly accentuated by the addition of a hydroperoxide scavenging system consisting of glutathione (1 mM) plus glutathione peroxidase (0.4 unit/ml). In contrast, addition of any of several hydroperoxides, i.e. 5-,8-,9- or 15-HPETE (EC50 ca. 1 microM), but not the corresponding alcohols (5-HETE and 15-HETE), shortened the lag phase. These results show that the 5-lipoxygenase requires hydroperoxide for activation and that cellular level of hydroperoxides may be an important factor regulating leukotriene synthesis.
R W Bryant; H S She; K J Ng; M I Siegel
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Prostaglandins     Volume:  32     ISSN:  0090-6980     ISO Abbreviation:  Prostaglandins     Publication Date:  1986 Oct 
Date Detail:
Created Date:  1987-02-04     Completed Date:  1987-02-04     Revised Date:  2003-11-14    
Medline Journal Info:
Nlm Unique ID:  0320271     Medline TA:  Prostaglandins     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  615-27     Citation Subset:  IM    
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MeSH Terms
Adenosine Triphosphate / pharmacology
Arachidonate 5-Lipoxygenase / metabolism*
Arachidonate Lipoxygenases / metabolism*
Arachidonic Acid
Arachidonic Acids / metabolism,  pharmacology*
Calcium / pharmacology
Clone Cells / drug effects,  metabolism
Cytosol / metabolism
Enzyme Activation / drug effects
Glutathione / metabolism
Mast Cells / drug effects,  metabolism*
Reg. No./Substance:
0/Arachidonic Acids; 0/Leukotrienes; 506-32-1/Arachidonic Acid; 56-65-5/Adenosine Triphosphate; 70-18-8/Glutathione; 7440-70-2/Calcium; 74581-83-2/arachidonic acid 5-hydroperoxide; EC 1.13.11.-/Arachidonate Lipoxygenases; EC 5-Lipoxygenase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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