Nomenclature-system, organization
International Union of Biochemistry Enzyme Commission
1. class of enzyme
2. sublclass
3. subsubclass
4. systematic name
1. class of enzyme
2. sublclass
3. subsubclass
4. systematic name
Classes of Enzymes and corresponding functions and numbers
1.oxidoreductases- ox-reduction rxns
2. transferases - transfer of functional groups
3. hydrolases- hydrolysis rxns
4. lyases - mediates double bond formation
5. isoberases - isomerization rxns
6. ligases- formation of bonds mediated by ATP cleavage
2. transferases - transfer of functional groups
3. hydrolases- hydrolysis rxns
4. lyases - mediates double bond formation
5. isoberases - isomerization rxns
6. ligases- formation of bonds mediated by ATP cleavage
Enzym specificity
Reaction
-absolute specificity (one specific substrate e.g. glucose oxidase works only on beta d glucose)
-group specificity (e.g. phosphatase)
-bond specificity-peptidase
Tissue
-what we worry about in clinic, enzymes being in the right place in right quantity. they all belong somewhere in some specific quantity.
-absolute specificity (one specific substrate e.g. glucose oxidase works only on beta d glucose)
-group specificity (e.g. phosphatase)
-bond specificity-peptidase
Tissue
-what we worry about in clinic, enzymes being in the right place in right quantity. they all belong somewhere in some specific quantity.
enzymes, energy of activation and transition state energy
Enzymes lower the activation energy by lowering the transition state energy. The enzyme allows for more efficient ways to get to the transition state.
Describe the Michaelis menten curve ([s] v. v}
as substrate concentration increases, the v approaches a v max because there is more substrate to turn over and not enough enzyme to turn it over quite as efficiently
What assumptions are taken in the michaelis menten equation?
in the equation E+2-> ES->E + P
K-2 is negligible and equilibrium is established rapidly.
these things only don't happen when the product starts building up (K-2 increases)
K-2 is negligible and equilibrium is established rapidly.
these things only don't happen when the product starts building up (K-2 increases)
Definition of Km
Michaelis menten constant
ES breakdown/ES formation or (k-1+K2)/K1
Numerically equivalent to the concentration of substrate at half of vmax.
Determined using the Lineweaver-Burk plot.
ES breakdown/ES formation or (k-1+K2)/K1
Numerically equivalent to the concentration of substrate at half of vmax.
Determined using the Lineweaver-Burk plot.
Lineweaver-Burk plot
Uses recipricals of values in M-M plot.
The Y- Intercept represents the reciprocal of vmax and the x intercept represents the negative reciprical of Km.
If y intercept dot moves up Vmax decreases
If X intercept dot moves to right, Km is increased, which means that more substrate is requried.
The Y- Intercept represents the reciprocal of vmax and the x intercept represents the negative reciprical of Km.
If y intercept dot moves up Vmax decreases
If X intercept dot moves to right, Km is increased, which means that more substrate is requried.
First order v. second order rxns
1st order: rate is less than v max and is dependent on substrate concentration. v increases linearly and does not approach vmax. Product formed forms curved plot, like approaching limit. Not enough substrate to always have some to convert
0 order: rate is not dependent on substrate concentration. as substrate concentration increases, vmax is reached. over time the amount of product increases linearly.
10-100x the Km value must be used to maintain 0 order rxn. (saturation kinetics)
We look at the 0 order rxn to determine rates.
0 order: rate is not dependent on substrate concentration. as substrate concentration increases, vmax is reached. over time the amount of product increases linearly.
10-100x the Km value must be used to maintain 0 order rxn. (saturation kinetics)
We look at the 0 order rxn to determine rates.
Factors affecting enzyme activity
Substrate concentration- must be in excess to maintain 0 order
product concentration- shifts equilibrium, causes same effect as substrate depletion if in excess
coenzyme concentration- Acts like substrate (NAD), if not enough of it behaves like substrate depletion ->1st order
concentration of Activators/cofactors- (Calcium, magnesium, vitamins) some systems require it to do anything, but if depleted causes 1st order
pH- Most enzymes prefer a fairly neutral pH (7-7.4), but sometimes they have much different pH's that they work at
Temperature- works best at 37 degrees C as temp increases, activity increases, but when the temp increases too uch the bonds deteriorate
Stability- stability of enzymes are variable, some need a specific temp (acid phosphatase) but others can sit for days (amylase)
Anticoagulant- should be avoided, they bind to Calcium and usualy Mg, use heperin in coagulations beause it doesn't use Ca
Hemolysis- enzymes reacting in plasma instead of cells, usually bec of bad collection
Inhibitors
product concentration- shifts equilibrium, causes same effect as substrate depletion if in excess
coenzyme concentration- Acts like substrate (NAD), if not enough of it behaves like substrate depletion ->1st order
concentration of Activators/cofactors- (Calcium, magnesium, vitamins) some systems require it to do anything, but if depleted causes 1st order
pH- Most enzymes prefer a fairly neutral pH (7-7.4), but sometimes they have much different pH's that they work at
Temperature- works best at 37 degrees C as temp increases, activity increases, but when the temp increases too uch the bonds deteriorate
Stability- stability of enzymes are variable, some need a specific temp (acid phosphatase) but others can sit for days (amylase)
Anticoagulant- should be avoided, they bind to Calcium and usualy Mg, use heperin in coagulations beause it doesn't use Ca
Hemolysis- enzymes reacting in plasma instead of cells, usually bec of bad collection
Inhibitors
Affect of competitive inhibition
binds to enzyme active site
Higher Km and same Vmax. needs more substrate to out number the inhbitors
creates X pattern, x intercept moves towards origin.
Vmax is unchanged.
This is how many therapeutic drugs work also methanol poisoning fixed by adding ethanol for alcohol dehydrogenase.
Higher Km and same Vmax. needs more substrate to out number the inhbitors
creates X pattern, x intercept moves towards origin.
Vmax is unchanged.
This is how many therapeutic drugs work also methanol poisoning fixed by adding ethanol for alcohol dehydrogenase.
Non competitive inhibition
Makes V shape
Lowers Vmax, Km unchanged.
Inhibitior binds to enzyme allosteric site
To stop this bind the inhibitor. chelate it. bind the inhbitior
e.g. lead poisoning is caused by lead binding to hemoglobin instead of iron. To get rid of it we synth enzymes to extract it.
Lowers Vmax, Km unchanged.
Inhibitior binds to enzyme allosteric site
To stop this bind the inhibitor. chelate it. bind the inhbitior
e.g. lead poisoning is caused by lead binding to hemoglobin instead of iron. To get rid of it we synth enzymes to extract it.
Uncompetitive inhbition
Parallele lines
decreases Km and dereases vmax.
inhibitor binds to ES complex.
using less substrate helps a little but not by much
decreases Km and dereases vmax.
inhibitor binds to ES complex.
using less substrate helps a little but not by much
International unity of activity (conventional)
U/L= amount of enzyme that will catalyze the transformation of one MICROMOLE of substrate PER LITER PER MINUTE under standard conditions
U/L= (delta A/sigma) X (1/time in minutes) X (total volume mL/ sample volume mL) X 10^6
delta A equals product formed.
WHEN ZERO ORDER
U/L= (delta A/sigma) X (1/time in minutes) X (total volume mL/ sample volume mL) X 10^6
delta A equals product formed.
WHEN ZERO ORDER
NAD / NADH and light absorption
both absorb light in 265 nm, but at 340 only NADH absorbs lights.
If you start with NAD and change to NADH the absorbance will increase with time. The more enzyme you have that converts it, the faster it will go.
IF you start with NADH and go to NAD the absorbance decreases with time and bottoms off when there's no more to convert.
If you start with NAD and change to NADH the absorbance will increase with time. The more enzyme you have that converts it, the faster it will go.
IF you start with NADH and go to NAD the absorbance decreases with time and bottoms off when there's no more to convert.
Isoenzymes definition
enzymes that exist in multiple molecular forms but catalzye the same chemical reaction
recombination of different subunites
e.g. LD
May have different physical biochemical, or immunologic properties
Synthessis may be organ specific
recombination of different subunites
e.g. LD
May have different physical biochemical, or immunologic properties
Synthessis may be organ specific
ways to separate isoenzymes
electrophoresis (fastest mover is isoenzyme one, substrate and inhibition specificity,heat stability, ultracentrifugation
plasma specific enzyme measurements
mainly produced by liver
specific functions in plasma (e.g. coag, lipoprotein lipase
If lipoprotein lipase is bad, triglycerine will build up and form lipemia
specific functions in plasma (e.g. coag, lipoprotein lipase
If lipoprotein lipase is bad, triglycerine will build up and form lipemia
non plasma specific enzymes measurements
typically low in plasma
if secretion increases it indicates leagage from cell injury
There is altered production in induced by alcohol (GGT) or as a tumor marker (LDH)
if secretion increases it indicates leagage from cell injury
There is altered production in induced by alcohol (GGT) or as a tumor marker (LDH)
clinical sensitivity
proportion of true positives, capacity to detct disease, no false negatives
TP/ (TP+FN) = sensitivity
TP/ (TP+FN) = sensitivity
clinical specificity
proportion of true negatives no false potsitives
spcificity = TN/ (TN+FP)
spcificity = TN/ (TN+FP)
Positive Predictive value
likelihood specific disease is present if test is positive/abnormal
Negative predictive value
likelihood a specific disease is absent if test is negative/normal
Nomenclature-system, organization
International Union of Biochemistry Enzyme Commission
1. class of enzyme
2. sublclass
3. subsubclass
4. systematic name
1. class of enzyme
2. sublclass
3. subsubclass
4. systematic name
Kartensatzinfo:
Autor: skunz11
Oberthema: Bio Chemisty
Thema: Acids
Veröffentlicht: 07.05.2010
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