Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
10 Cards in this Set
- Front
- Back
|
The Ergosterol System |
Ergosterol is the 'cholesterol' equivalent in Fungi Cell walls. Squalene --> Lanesterol ---> Ergosterol |
|
|
What class of drugs inhibits squalene oxide? |
Allylamines. e.g. Naftifine and Terbinafine Squalene synthesis inhibition stops lanesterol being made |
|
|
What class of Drugs targets the enzymes: 14 alpha demethylase 4 alpha demethylase delta 22, 23 desaturase |
The Azoles. Triazoles target all, Azoles target the two demethylase enzymes. E.g. econazole, Miconazole, bitertanol |
|
|
What class of drugs targets the enzymes: delta 7 delta 8 isomerase delta 14 reductase |
Morpholines e.g. Amorolfine |
|
|
Why are 5 membered rings better than 6 membered rings in the inhibition of enzymes responsible for ergosterol synthesis? |
5 membered rings containing N are Sp3 hybrodized whereas 6 membered rings have sp2 hybrodization. The N group has better affinity for the Fe atom in the cytochrome p450 enzyme. |
|
|
How does the enzyme get inhibited? |
The cytochrome P450 enzyme contains a haeme group. The Fe atom is bound to a cysteine ligand and works by binding to the methyl group on the lanesterol. A series of reactions takes place where this methyl group is removed (demethylated). The N group on the Azole or pyrimidine group binds to the Fe instead of the CH3 inhibiting the demethylation step. |
|
|
How does AMP-b work? |
Amphoteracin b is a very toxic fungicide. works by binding to ergosterol which formed a channel in the membrane of the fungal cell. this caused leakage of the monovalent ions (k+, Cl-, H+ and Na+) which leads to cell death. AMP b can be very toxic in humans as humans also contains sterols. |
|
|
What components make up the cell wall of a fungi? |
Mannoproteins, B 1,6 glucans, 1,3 glucan synthase, ergosterol, chitin |
|
|
What are the potential cell wall targets for antifungal treatments? |
Chitin synthase, 1,3-B-D- glucan synthase, Chitinase |
|
|
What is chitin? |
a component of the cell wall. Can be compared to keratin, a hard substance found in crab shells and insect exoskeletons. In fungi it helps strengthen the cell wall. |
