inhibitors Flashcards
how do competitive inhibitors work?
- bind to active site since they have similar shape to substrate, temporarily prevent ESC’s from forming until released
- increasing substrate concentration decreases their effect
how do non-competitive inhibitors work?
- binds at allosteric binding site
- trigger conformational change of active site
- increasing substrate concentration has no impact on their effect
what is end-product inhibition?
one of the products of a reaction acts as a competitive or non-competitive inhibitor for an enzyme involved in the pathway -> this prevents further formation of products
what are irreversible inhibitors? give an example
- permanently prevent formation of ESC’s
- heavy metal ions e.g. mercury, silver, cause disulphide bonds in tertiary structure to break
- bind to enzymes by strong (covalent) bonds e.g. cyanide binds to cytochrome c
what are reversible inhibitors?
- may be competitive or non-competitive
- bind to enzyme temporarily e.g. by H-bonds or a few ionic bonds
- ESC’s can form after the inhibitor is released
define metabolic poison
- substance that damages cells by interfering with metabolic reactions
- usually an inhibitor
give some examples of metabolic poisons and describe them
respiratory inhibitors include:
- cyanide: non competitive, irreversible, inhibits cytochrome c oxidase
- malonate: competitive, inhibits succinate dehydrogenase
- arsenic: competitive, inhibits pyruvate dehydrogenase
how do some medicinal drugs act as inhibitors?
penicillin: non-competitive inhibitor of transpeptidase to prevent formation of peptidoglycan cross-links in bacterial cell wall
ritonavir: inhibits HIV protease to prevent assembly of new virions
what are inactive precursors in metabolic pathways?
- to prevent damage to cells, some enzymes in metabolic pathways are synthesised as inactive precursors e.g. proteases
- one part of the precursor acts an inhibitor
- ESC’s form when it is removed
