S4- Enzymes Flashcards
2 enzyme cofactors are:
Vitamins and essential metals
4 types of metal ion functions as enzyme cofactors:
- Major minerals included in structure of enzymes (Mg2+/ Ca2+) and trace elements (Cu2+, Zn2+, Fe2+/3+, Mn2+ and Mo4+)
- Part of active site/ involved in electrostatic substrate binding (Zn2+ in carbonic anhydrase, Mg2+ in kinases)
- Act as redox agents (Fe2+/3+ in cytochrome)
- Regulate activity of enzymes (binding= less/more active form of enzyme)
How is Zn2+ involved as cofactor in transport of CO2 to lungs?
CO2 dissolves in blood as hydrogen carbonate (H2CO3)
It reacts with H2O
Zn2+ in carbonic anhydrase enzyme active site= binds to H2O and activates it for reaction with CO2
Many water-soluble…are essential coenzymes
They function as…
Ie:
Vitamins
Carriers of reaction components
- Coenzyme A= acyl units
- NADPH and FADPH2= carry electrons
- Biotin (vitamin B) and thiamine pyrophosphate (vitamin B1)= carry CO2
2 examples of mutations in enzyme genes:
- Glucose-6-phosphate dehydrogenase (G6PDH)= deficiency causes metabolic defect (cell membrane cannot repair itself)
- Thiopurine methyl transferase (TPMT) preventing successful response (adverse response) to cancer chemotherapy
G6PDH deficiency is the most…
It is…recessive
(High incidence in malarial regions)
Symptoms are…
Can be triggered by…
Common enzyme defeciency
X-linked
Haemolytic crisis, jaundice, brain damage in infants
Drugs, foods, infections
The 3 pathways by which glucose is used in body:
NADPH is made through…pathway
Enzyme…is needed to make NADPH
- Glucose-> glucose 6 phosphate->glycolysis ->energy
Glucose-> glucose 6 phosphate-> pentose phosphate pathway-> 1. Ribose 5 phosphate-> nucleic acid
2. NADPH-> fuel biosynthesis
Pentose phosphate
G6PDH
NADPH is needed to make….which repairs…
RBC are dependant on…to make NADPH because…
Glutathione
Damaged cell membrane lipids (by oxidation)
G6PDH, they don’t have mitochondria
The enzymes in lipid membrane repair mechanism based on reduction are:
- Glutathione peroxidase (=oxidised glutathione + water and R-OH)
- Glutathione reductase (NADPH used-> reduced glutathione made)
Possible treatment for malaria…which increases…conc
This kills pathogen and damages the membrane even more but its okay since it will….
But in G6PDH deficiency, the RBC will not be able to….so people with deficiency will react…to the drug
Primaquine stimulates
H2O2
Repair itself
Repair its membrane
Badly
6-MP is a…used in cancer treatment that results in…
It can be metabolised via…
TPMT metabolism pathway results in….
Prodrug
Cell death
2 pathways
Inactivation of the drug
TPMT has 3 types of activity in the body because it is influenced by….
Who to give the highest/ lowest drug dose to..
How many copies of the low/high alleles you have
L/L = lowest activity= lowest drug dose
L/H = medium activity= medium drug dose
H/H = highest activity= highest drug dose
5 levels of enzyme activity control are:
- Inhibition (reversible/ irreversible)= serine protease inhibitors (serpins)
- Feedback regulation (4 examples)
- Covalent modification= protein phosphorylation
- Proteolytic activation= of inactive ‘zymogens’ (trypsin, blood clotting)
- Allosteric effectors
3 examples of serine protease inhibitors:
- Alph antitrypsin (anti elastase)= stop protease from attacking tissue
- Pancreatic trypsin inhibitor= control activity of digestive enzymes
- Antithrombin III= switch off blood clotting
4 examples of feedback regulation (some products in chain of enzyme reaction stimulate or inhibit some previous enzymes to make the right amount of products):
- Energy metabolism pathway
2.NADP+ on G6PDH - Purine biosynthesis
- Amino acid biosynthesis
