Lec 11 and 12: Enzymes I and II Flashcards
what is the function of the enzyme papain?
break any peptide
what is the function of the digestive enzyme trypsin?
only splits bonds between lysine and arginine residues
what is the function of the enzyme thrombin?
catalyses the hydrolysis or Arg- Gly only in a specific chain of residues
what are the three major examples of proteolytic enzymes?
papain, trypsin, thrombin
what are cyclins?
family of proteins that
control the progression of cells through the cell cycle by activating cyclin-dependent kinase (Cdk) enzymes.
what is a cofactor?
non-protein chemical compound or metallic ion that is required for a protein’s biological activity to happen.
what is an apoenzyme?
an enzyme without its cofactor
what is a haloenzyme?
an enzyme with a cofactor q
what are examples of cofactors?
Zn Cu,Fe
how do cofactors affect an enzyme?
- Make it fold and create an active site
- Enhance the charge in the active site to improve substrate binding
which cofactor does amylase require?
chloride ions
what is a coenzyme?
Small organic molecules attach to activate the enzyme and detach when reaction completed to deactivate the enzyme
what are examples of coenzymes?
vitamins such as niacin, riboflavin
what are isozymes? (like isomers)
enzymes that differ in amino acid sequence but catalyse the same chemical reaction.
how are isoenzymes different and what is their main role?
they display different kinetic parameters (e.g. different Km values), or different regulatory properties.
isozymes permits the fine-tuning of metabolism to meet the particular needs of a given tissue or developmental stage
what enzyme is linked to hurler syndrome?
what does this disease cause?
defiency in iduronidase
hurler syndrome= abnormal bone structure and developmental delay
In the hurler syndrome disease what are the types of severities?
Severe –> less severe
Hurler –> hurler scheie –> scheie
which enzyme is linked to Niemann-Pick disease
what does the disease cause?
a lack in acid sphingomyelinase (ASM)
affects lysozymes
causes malfuncttion of major organ systems
which enzyme is linked to Tay sachs disease?
what does the disease cause?
hexosaminidase-A that is absent from lysosymes
results in deterioration of nerve cells, mental and physical abilities
which enzyme is linked to the disease homocystinuria
what does the disease cause?
Cystathionine beta-synthase
homocysteine amino acid and toxic by-products build up in the blood
bad eye sight, osteroporosis
(weakening of the bones)
*NOTE* labelling an enzyme
what are the 6 types of oxidoredcutases?
state what each one does
hydroxylases: add hydroxyl groups to subs (OH)
oxidases: intramolecular oxygen that accepts H/e-
peroxidases: reduction of H2O2
reductases: catalyse reductions
oxygenases: incoporate intramolecular oxygen into organic subs
dehydrogenases: oxidise substrate by transferring one or more hydride ion H-
what is the function of transferases? given an example
that catalyse the movement of a functional group from one molecule to another. e.g methyl, phosphate, glycosyl grouyps
e.g human kinase
what is the function of lyases?
what are the three types of lyases?
catalyse lysis reactions that generate a double bond.
- carboxylases: add or remove COOH groups
- aldohases: cleaved an aldol
- dehydratases: remove oxygen or hydrogen in the form of H2O
what is the function of isomerases enzymes?
catalyse structural changes within a molecule.
only one substrate and one product with nothing gained or lost,
so they represent only a change in shape.
what is the function of ligases?
catalyses ligation: the joining of two substrates
reaction is coupled to the hydrolysis of a disphosphate bond in ATP.
what is the function of hydrolases?
what is the difference between endo and exo enzymes?
Catalyse hydrolysis; the breaking of single bonds through the addition of water.
endoenzymes cut in the middle of the chain whereas exo enzymes cut at the end of the chain to release an individual monomer.
what are the three types of hydrolases enzymes?
Proteases/ peptidases: cleave peptide bonds between amino acids in order to breakdown proteins
Lipases: break down lipids into fatty acids and glycerol by cleaving ester bonds
Nucleases: cleave phosphodiester bonds between nucleotide subunits in nucleic acids
what is the unit for enzyme activity?
μmol/min/mg of protein
or
IU/mg
why is enzyme velocity measured at time 0?
prevents observed effects by feedback inhibition or reversible reactions
what is the unit for the amount of enzyme which catalyses conversion of 1um of substrate per minute
1IU = 1μmol/min
what is michaelis-menten enzyme kinetics?
The study of the rate of an enzyme controlled reaction (to see the effect of substrate concentration, of different inhibitors/drugs or different isozymes/mutations
what is the michaelis-menton eqaution
what is km used to ditinguish between?
isoenzymes
what are the two types of reversible inhibition?
competitive and non-competitive
what type of inhibitor is disulfiram antabuse?
a competitive inhibitor
what is the antitode for methanol poisioning?
how does this chemical work?
ethanol
acts as a competitive inhibitor
what type of inhibitor is nifediphine?
a non-competitive (allosteric) inhibitor
prevents the uptake of calcium ions into cardiac cells to treat agina and high blood pressure
what type of inhibition is shown in this lineweaver-burk plot?
competitive inhibition
because Km is increased (substrate is more at 50%) but Vmax is unaffected (saturation point is still the same)
what type of inhibtion is shown in this lineweaver-burk plot?
uncompetitive inhibition
Km reduced
Vmax is reduced
what type of inhibition is shown in this lineweaver-burk plot?
Noncompetitive
Km is unaffected (substrate level is still the same at 50% of Vmax)
Vmax reduced (saturation point is lowe)
what are Irreversible inhibitor
give an example
substances that bind so tightly to the enzyme (by a covalent bond) that they cannot be removed
e. g. Sarin binds to serine preventing nerve impiulse transmission
e. g. aspirin reducing synthesis of inflammatory signals
what is uncompetitive inhibition?
known as anti-competitive inhibition, takes place when an enzyme inhibitor binds only to the complex formed between the enzyme and the substrate (the E-S complex
what type of inhibitor is lithium?
what does it do?
lithium is an un-competitive inhibitor
used to treat manic-depressive psychosis
what is end product inhibition?
aka feedback inhibition
where the reaction product inhibits the enzyme acitivity
What does the inhibitor often bind to during feedback inhibition?
the allosteric site of the enzyme being inhibited
what are zymogens?
any of a group of proteins that display no catalytic activity but are transformed within an organism into enzymes
how does ELISA work?
ELISA: enzyme-linked immunosorbent assay
- Primary antibody against antigen of interest is coated on 96well plate
- Patient sample is added
- Antigen binds to primary antibody
- Washing removes unbound antigen
- Secondary HRP conjugated antibody to antigen is added
- Colour develops by adding HRP substrate
why are 2 types of antibodies needed in indirect ELISA?
primary antibodies immobilise the antigen
the secondary antibodies is used for the detection of the antigen
