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S1B4: Biochemistry > Eicosanoid Metabolism I > Flashcards

Eicosanoid Metabolism I Flashcards

1
Q

Where is omega-6 fatty acid found?

What is the most common omega-6 fatty acid? What can this be converted to?

A

vegetable oils, nuts and seeds

linoleic acid, which can be converted to arachidonic acid

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2
Q

How many carbons compose eicosanoids?

Which fatty acids are required for their synthesis?

What is special about these fatty acids?

A

20

omega-3 (18:3 9/12/15) and omega-6 (18:2 9/12) fatty acids are required for their synthesis

they must be consumed from the diet (cannot be synthesized)

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3
Q

Synthesis of arachidonic acid

A
  • linoleoyl CoA is de-saturated at carbon 6
  • elongated 2 carbons by malonyl CoA
  • desaturated at carbon 5 = aracidonyl CoA
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4
Q

What is the function of eicosanoids?

A

most potent regulators of cellular function

act at “local” hormones

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5
Q

the activation of which phospholipase is responsible for the release of arachidonic acid from phospholipid membranes?

A

A2

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6
Q

How would the body inhibit inflamation during and immune response?

A

glucocorticoids inhibit phospholipase A2

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7
Q

What is the enzyme responsible for producing prostaglandins from arachidonic acid?

Which molecule inhibits this enzyme?

A

cyclo-oxygenase

inhibited by aspirin and other NSAID

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8
Q

Which type of tissues primarily synthesize prostaglandins?

Which type of tissues priamrily sunthesize thrombaxane A2?

A

vascular endothelial

platelets

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9
Q

active prostoglandins contain how many carbons?

how many internal rings?

Hydroxy groups?

Double bonds?

A

20 carbons

5 internal rigns

Hydroxyl at carbon 15

double bond between 13 and 14

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10
Q

What do the number subscript identify in prostaglandin classification?

What do the greek subscript describe?

A

the number indicates the number of double bonds

the greek subscript indicates the position of the hydroxyl group on carbon 9 found on PGF

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11
Q

How does the structure of thromboxane differ from that of prostaglandins?

What is the most common thromboxane? How is its structure different?

A

thromboxanes contain a 6 member ring that includes an oxygen

TAX2–Additional O atom attached to C9 and C11 of the ring

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12
Q

Synthesis of prostaglandins and thromboxanes from arachidoic acid.

A
  • The 5 membered ring is formed and 4 oxygen are added (2 at C15, and two between C9 and C11)
    • this produces PGG2, a very unstable intermediate
  • Peroxidase reduces the hydroperoxy at C15 to an alcohol
    • producing PGH2
  • various enzymes acti on PGH2 to produce specific thromboxanes or prostaglandins
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13
Q

Which biocompounds

  • increase:
    • vasodilation
    • cAMP
  • decrease
    • platelet aggregaion
    • leukocyte aggregation
    • IL-1 and IL-2
    • T-cell proliferation
    • Lymphocyte migration
A

PGI2, PGE2, PGD2

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14
Q

Which biocompound

  • vasoconstriction
  • bronchoconstriction
  • smooth muscle contraction
A

PGF2alpha

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15
Q

Which biocompound

  • increases
    • vasoconstriction
    • platelet aggregation
    • lymphocyte proliferation
    • bronchoconstriction
A

Thromboxane A2

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16
Q

What is the difference betwen COX-1 and COX-2?

A
  • COX-1
    • constitutive (low level)
    • Housekeeping functions
      • platelet regulation (blood clotting)
      • kidney function
      • regulation of stomach/mucous production
  • COX-2
    • inducible (acute high level)
    • inflammation
      • heat
      • swelling
      • pain
17
Q

Which class of drugs block cyclooxygenase? What is an example of this drug?

How does it work?

A

NSAID

aspirin (irreversible) ibuprofen (reversible)

transfers an acetyl group to COX (irreversibly inhibiting it)

18
Q

What is a complication of NSAID drugs?

A

they inhibit both COX-1 and COX-2, blocking housekeeping functions

gastrointestinal and platelets effects

19
Q

What are negative impact of long-term COX-2 inhibitor use?

A
  • negative effects on cardiovascular function
  • alters balance of prostacyclin and thromboxane b/c platelets (major source thromboxane) do not have COX-2 receptors, so thromboxane synthesis is not decreased
20
Q

How are thromboxanes and prostaglandins inactivated?

What is their approximate length of half life?

A
  • prostaglandin
    • inactivated by oxidation of C15 hydroxyl, reducing the double cond at C13, bet and omega oxidation –> increases in the urine
  • Thromboxane
    • cleavage of the oxygen bridge between C9 and C11 –> TXB2 (no biologic activity)

t 1/2 = seconds to minutes

21
Q

What are the 2 types of receptors that eicosanoids can bind to?

A

stimulatory or inhibitory

22
Q

Provide a paracrine and autocrine example for TXA2 function

A
  • paracrine
    • contraction of vascular smooth muscle caused by TXA2 released from platelets
  • autocrine
    • platelet aggregation induced by TX2A produced by the platelets themselves

S1B4: Biochemistry (7 decks)

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