Question | Answer |
How do leukotrienes differ from prostaglandins, prostacyclins, and thromboxanes? | linear eicosanoids, not cyclic |
What is the role of leukotrienes? | mediate allergy response, immunity, inflammation |
What is the most serious leukotriene that causes a response 10,000 times (5 orders of magnitude) greater than histamine? | peptidoluekotriene |
Peptidoleukotrienes are known to be the active component of what mediator of intense, violent, often fatal allergic rxns? | slow-reacting substances of anaphylayxis (SRS-A) |
What is the common predominant precursor between cyclic eicosanoids and linear eicosanoids? | arachidonic acid |
The first step of Arachidonic acid metabolism is it's conversion by what to what? | Lipoxygenases (LO) convert it to 5HPETE: hydroperoxyeicosatetraenoic acids |
What final products do the three types of lipoxygenases create? | 5-LO = leukotrienes, 15-LO = lipoxins, 12-LO = hepoxilin |
AFter conversion to 5-HPETE, what does 5LO create in it's second catalyzation? | 5-HPETE to Leukotriene A4 - the parent leukotriene |
What must also be present to assist 5LO? | FLAP - 5-lipoxygenase activating protein |
What are the two reactions of 5LO? | adds Ox to arachidic acid to make 5-HPETE
then, acts as endoperoxidas to remove water and create an double attached Oxygen, peroxy? which is Leukotriene, A4 |
What special trait does LTB4 exhibit? | Chemotactic, attracts immune cells to fight infections |
What important antioxidant is needed as a substrate for LTA4 to convert to other actives such as LTC4, LTD4, LTE4 | glutathione via glutathion-S-transferase |
What do LTC4 and LTE4 do? | peptidoleukotrienes - they are the actual bad ones - SRS-A's of astma and inflamation |
What is important about omega-3 fatty acids in our diet? | They form eicosapentaenoic acid (EPA) prostaglandins and leukotrienes derived from them are less physiologically active - decreased inflammation etc.. |
What are the Series Number associated with prostaglandins and leukotrienes derived from arachadonic acid? | Prostaglandins = series 2
Leukotrienes = series 4 |
What are the Series Number associated with prostaglandins and leukotrienes derived from eicosapentanoic acid (EPA)? | Prostaglanidin = series 3
Leukotriene = series 5 |
What are the Series Number associated with prostaglandins and leukotrienes derived from eicosatrienoic acid (ETA)? | Prostaglandins = series 1
Leukotrienes= series 3 |
PGH2 synthase is a multifunctional enzyme with two active sites. What operates at each? | One = cyclooxygenase (COX)
Two = endoperoxidase |
How are lipoxins different from other eicosanoids? | The are ANTI-inflammatory agents |
How do we synthesize lipoxins? | 15-LO |
Why do we still think of arachidonic acid in terms of inflammation if it also makes lipoxins? | Prostaglandin synthesis is greater than lipoxin synthesis. |
How does aspirin over come the prostaglandin/lipoxin imbalance? | Aspirin is a suicide inhibitor of the PGH2 pathway. It ihibits COX 1 and COX2, but does not inhibit endoperoxidase at the second active site on PGH2-synthase. So 15-HPETE can make 15-epi-LXA4, which is a version of lipoxin. |
What are aspirin-triggered epilipoxins? | enantiomers of 15S-HPETE formed when aspirin blocks the COX active site, but does not affect the endoperoxidase site on PGH2-synthatse |
The pharmaceutical industry produces an agent that targets receptors How? | inhibit release of arachidonic acid from phosphatidyl insositol by steriods that block Phospholipase A. |
What drugs target leukotriene action by inhibiting LTC4-receptors? | Montelukast (singular)
Zarfilukast (Accolate) |
What drug inhibits 5-LO? | zileuton (Zyflo) |
What drug inhibits FLAP | MK0886 |