5-lipoxygenase and LTA synthase exist as a multienzyme complex
The first step in the biosynthetic pathway for leukotrienes is the oxidation of arachidonic acid to 5-hydroperoxyeicosa-tetraenoic acid (5-HPETE) catalyzed by 5-lipoxygenase. The 5-HPETE then partitions between reduction by glutathione to 5-hydroxyeicosatetraenoic acid (5-HETE) and dehydration to leukotriene A4 (LTA-4). In studying LTA-4 formation in lysates of rat neutrophils, the authors have obtained kinetic evidence that 5-lipoxygenase and LTA synthase form a multienzyme complex. When 10 ..mu..M arachidonic acid is added to lysates, transient accumulation of 5-HPETE is detectable and varies between 4 ..mu..M and less than 0.5 ..mu..M depending on the concentration of glutathione in the assays. Despite the wide variation in 5-HPETE levels, a constant 2.5 +/- 0.4 ..mu..M LTA-4 is formed in a burst as arachidonic acid is consumed. In addition, when (/sup 3/H)arachidonic acid and 5-(/sup 1/H)HPETE are added simultaneously to lysates in the absence of glutathione, the specific activity of the LTA-4 that is initially formed is the same as that of the arachidonic acid undiluted by the 5-(/sup 1/H)HPETE. These two results together require that LTA-4 can be efficiently formed from a pool of 5-HPETE that is neither free in solution nor accessible to reduction. A model in which LTA synthase and 5-lipoxygenase form a multienzyme complex would explain efficient shuttling of 5-HPETE directly from one enzyme to the other and would predict the above observations. Copurification to near homogeneity of these two enzymes has now been achieved and is evidence for their physical association.
- Research Organization:
- Merrell Dow Research Institute, Cincinnati, OH
- OSTI ID:
- 7246678
- Report Number(s):
- CONF-8606151-; TRN: 86-039058
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 45:6; Conference: 76. annual meeting of the Federation of American Society for Experimental Biology, Washington, DC, USA, 8 Jun 1986
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ARACHIDONIC ACID
METABOLISM
LIGASES
BIOCHEMICAL REACTION KINETICS
OXYGENASES
BIOLOGICAL PATHWAYS
GLUTATHIONE
NEUTROPHILS
RATS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
ANIMALS
BIOLOGICAL MATERIALS
BLOOD
BLOOD CELLS
BODY FLUIDS
CARBOXYLIC ACIDS
DRUGS
ENZYMES
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
LEUKOCYTES
MAMMALS
MATERIALS
MONOCARBOXYLIC ACIDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDOREDUCTASES
PEPTIDES
POLYPEPTIDES
PROTEINS
RADIOPROTECTIVE SUBSTANCES
REACTION KINETICS
RODENTS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques