Enzymes Flashcards
What are the six major classes of enzymes?
oxidoreductases transferases lyases hydrolases isomerases ligases
What do oxidoreductases do and give an example of one
catalyse redox reaction
e.g. lactate dehydrogenase
What do transferases do and give an example of one
transfer functional groups
aminotransferase
What do lyases do and give an example of one
add/remove atoms/functional groups to/from C=C/rings
decarboxylases
What do hydrolases do and give an example of one
cleave molecules by adding water
trypsin
What do isomerases do and give an example of one
catalyse the conversion of a molecule to one of its isomers
triose phosphate isomerase
What do ligases do and give an example of one
GLUE!!
join 2 molecules together
DNA ligase
What are co-factors and co-ezymes?
they help out enzymes that cannot carry out catalysis alone
What is the difference between co-enzymes and co-factors? Give examples of each
Co-factors directly assist with the reaction, e.g Mg2+ with DNA polymerase in DNA replication
Co-enzymes are organic carrier molecules which carry things needed for the catalysis, e.g. NADH - carry electrons, CoA - carry Acetyl groups
What is the difference between Vitamins and Minerals?
They are both types of co-enzymes and co-factors but:
Vitamins are organic, e.g. B3, B5
Minerals are inorganic, e.g. Mg2+, Ca2+
What is notable about pancreatic serine proteases?
The proteases in this group are all similar but catalyse hydrolysis at DIFFERENT POSITIONS in the peptide sequence due to structural differences in the polypeptides
What are the 3 well known enzymes that go through the serine protease mechanism?
CHYMOTRYPSIN
TRYPSIN
ELASTASE
What are the 6 types of enzyme regulation?
Gene Expression Feedback loop Feed forward activation Allosteric regulation Phosphorylation/Dephosphorylation Proteolysis
What is meant by irreversible inhibition?
an irreversible inhibitor reacts with the enzyme making it enzymatically inactive and the active enzyme cannot be regenerated
What is meant by reversible inhibition?
A reversible inhibitor can bind to the enzyme and then be released leaving the enzyme in its original condition.
There are 3 types.
What are the 3 types of reversible inhibition? Briefly explain each of their action.
Competitive - compete with the substrate for the active site as it is similar in shape/structure. Increasing substrate competition decreases effect of inhibitor.
Non-competitive -binds to an allosteric site and changes conformation of active site. Cannot be overcome by increasing substrate inhibition.
Un-competitive - inhibitor binds to enzyme-substrate complex only - a binding site is created for the inhibitor when the substrate binds to the active site.
What are the 3 types of enzymes used as drug targets?
INHIBITORS - ACE is used to treat hypertension
FALSE SUBSTRATES - producing an abnormal metabolite,
FLUOROURACIL
PRO-DRUGS - an inactive precursor is given which is then converted into its active form by the enzyme, CORTISONE to HYDROCORTISONE
How are enzymes used a markers for disease?
Enzymes are generally intracellular and predoninantly located in one/a small number of organs so their release into the bloodstream can be used as a marker of cell damage/cell death
What are isozymes?
isozymes are isoforms of enzymes which catalyse the same reaction but have different properties and structure.
What are the 3 known possibilities for isozyme formation?
They may be:
- synthesised during different stages of foetal/embryonic development
- present in different tissues
- present in different cellular locations
Give details of the isozymes of Creatine Kinase
CK is a dimeric protein which binds to the muscle sarcomere.
MM = skeletal muscle BB = brain MB = heart
indicates skeletal muscle damage
Give details of the izosymes of Lactate Dehydrogenase
Enzyme has 4 subunits so there are 5 different combinations.
Found in heart, kidneys, RBCs, Liver and Skeletal Muscle.
increase in LDH indicates tissue damage + location. Also used to look at disease progression.
