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protein catalyst in biological systems

International Union of Biochemistry Enzyme Commission

1. class of enzyme
2. sublclass
3. subsubclass
4. systematic name

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

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.

Enzymes lower the activation energy by lowering the transition state energy. The enzyme allows for more efficient ways to get to the transition state.

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

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)

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.

v= (vmax) x ([s]/(Km+[s])

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.

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.

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

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.

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.

Parallele lines
decreases Km and dereases vmax.
inhibitor binds to ES complex.
using less substrate helps a little but not by much

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

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.

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

electrophoresis (fastest mover is isoenzyme one, substrate and inhibition specificity,heat stability, ultracentrifugation

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

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)

proportion of true positives, capacity to detct disease, no false negatives

TP/ (TP+FN) = sensitivity

proportion of true negatives no false potsitives

spcificity = TN/ (TN+FP)

likelihood specific disease is present if test is positive/abnormal

likelihood a specific disease is absent if test is negative/normal

International Union of Biochemistry Enzyme Commission

1. class of enzyme
2. sublclass
3. subsubclass
4. systematic name