Enzymes And RegulationOf Enzyems Flashcards by Sophia Skedros

All enzymes are proteins except

Ribozymes
-this is a catalytic ribonucleic acid triggering catalysis of RNA processing

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Enzymes ___ transition state

Stabilize

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If there were no enzyme how would the reaction proceed

Super slow or not at all
And it would take a tonnnn more energy

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Εnzymes change the ____ energy but not the ______ energy

Activation

Overall

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Enzymes _____ the rate of exergonic reactions by lowering the _______

Increase

Activation energy of the reaction

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What 2 models describe the way enzymes work with substrates

Lock and key

Induced fit

See slide 8 W7

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Which model is more common

Induced fit

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What do enzymes need for catalysis

Active sites aka groove aka cleft

Cofactors - metal ions

Coenzymes - prosthetic groups

Compartmentalization

Specificity

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Steps of induced fit

1 - enzyme active site has AA lining it

2 - the substrate binds (ES complex)

3 - additional bonds are formed to make the fit better (transition-state complex)

4 - products produced

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Cofactors for enzymes are

Metal ions - which are INORGANIC

Small, non protein

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Coenzymes for enzymes are

Prosthetic groups - tightly bound, does not dissociate away from enzyme

and co-substrates - associates with enzyme TEMPORARILY

They are ORGANIC

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Cofactor examples

Mg, K, Ca, Zn, Fe, Cu

They are bond with enzyme molecule

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Coenzymes examples

Vitamins!!!

NAD - B3/niacin
FAD - B2/riboflavin
Coenzyme A

Bind TEMPORARILY or permanently to enzyme NEAR active site

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Water soluble vitamins are

Coenzymes

Thomas
Richard
Never
Pounded
PussySix
But
fondled
Chest

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Enzymes need to be compartmentalized ___

Within the cell

Want to be in the ideal space for substrate + enzyme meeting

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Enzymes have substrate specificity. Give 3 examples

Chymotrypsin has a hydrophobic active site for aromatic AA: trp, tyr, phen

Trypsin has a “-“ active site for “+” AA: lys, Arg

Elastase has a narrow active site for small uncharged AA: gly, ala, ser

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What are the 3 types of enzymes

Isozymes

Allosteric enzymes

Proenzymes

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Define isozyme

Multiple forms of an enzyme that catalyze the same reaction

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Define allosteric enzymes

Multisubunit enzyme with identical or different polypeptide chains

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Define proenzymes

biologically inactive substance which is metabolized into an enzyme

Zymogen -pancreas

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What affects the activity of enzyme rxn and influence rate of rxn

pH
Temp
Substrate conc/enzyme conc

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What enzyme will activity will go up at acidic levels

Pepsin

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what enzyme will go up at pH 7

Salivary amylase

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What enzyme will go up at pH 9.5

Arginase

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If temp is too low what happens to rate of enzyme activity

INACTIVE

If temp is too high what happens to rate of enzyme activity

Denatured

Which has a higher affinity for glucose hexokinase or glucokinase

HEXOKINASE

What would utilize hexokinase

Brain cuz it NEEDS glucose

Where is glucokinase found

Liver Parenchyma cells Pancreatic islet cells

What is the KM of hexokinase if we know it has a high affinity for glucose

0.1mM This makes sure a supply of glucose for tissues is there even when the blood glucose is low

What is the KM of glucokinase if we know it has a low aff for glucose

10mM This is 100x less aff compared to hexokinase

KM vs KD

KM = Michaelis constant Kinetic constant NOT equilibrium constant Shows the affinity of substrates binding for the active site KD = dissociation constant thermodynamic constant Equilibrium constant Shows the affinity of the ligand towards an enzyme

What changes enzymes rate (regulates)

1. Substrates/inhibitors 2. Allosteric regulation of enzymes 3. Covalent modification of enzymes via hormonal reg

Allosteric enzymes have _____ sites and _______. They show _______. And display ____ on a graph

Multiple active sites, change their conformation after they bind Cooperative binding Sigmoidal dependence

Where does an allosteric enzyme that causes inhibition and activation bind

NOT at the active site

___ are metabolic inhibitors or activators that affect activity of allosteric enzymes

Effectors

Positive Effectors characteristics

Once it binds it changes both subunits to a higher affinity for Shifts graph to the left Activators bind more tightly to R state

Negative effector characteristics

Binding both subunits to a low affinity form which inhibits activity Bind more tightly to Tstate

____ is a good example of allosteric effects

Hemoglobin

Sigmoidal shape in allosteric curve is due to

Conformation change in enzyme The cooperative binding

What is a common way to quickly adjust activity of enzymatic reactions

Covalent modification

Covalent modification is

Usually reversible Phosphorylation CAMP

Adding or removing phosphate groups is an example of

Covalent modification

Substrate availability results in _____ and take ______ long

Change in velocity Seconds

Product inhibition results in ____ and takes ____ long

Change in Vm and/or Km Seconds

Allosteric control results in _____ and takes _____ long

Change in Vm and/or Km Seconds

What kind of bond is allosteric control utilizing

Non-covalent

Covalent modification results in ____ and takes ___ long

Change in Vm and/or Km Seconds to minutes

Induction or repression results in ____ and takes ____ long

CHANGE IN AMOUNT Min to hrs to days

Which regulator does not affect rate of reaction Substrate availability Allosteric control Induction or repression Covalent modification Product inhibition

Induction or repression. It changes the amount of enzyme

Allosteric control effects

End product

Covalent modification affects

Another enzyme

Induction or repression effects

Hormone/metabolite

Induction or repression can alter

Protein sythesis It takes a long time cuz its DNA and RNA

_____ resemble the substrate and bind reversibly at the active site

Competitive inhibitors

____ bind to the enzyme reversibly in a different domain than the active site changing the conformation of the enzyme

Non competitive inhibitors

What does a comp. Inhibitor effect

Raises the KM Because you need more substrate to fight for spots Vmax stays the same

What does a non competitive inhibitor effect

Lowers the vmax KM stays the same Cuz no one is interfering with the active site

What does uncompetitive inhibition effect

BOTH Km and Vmax

Lovastatin is an example of a _____ inhibitor. It effects the substrate ___

Competitive HMG CoA It decreases lipids

____ is an example of a non competitive inhibitor to pyruvate kinase

Alanine

Silver poisoning is an example of __

Non competitive inhibition

Examples of uncompetitive inhibition

Inhibition of Arya sulphatase by hydrazine Inhibition of intestinal alkaline phosphatase by phenylalanine

What is the end result of a suicide inhibitor

Fewer enzyme molecules active to catalyze norm reactions - the vmax decreases

Suicide inhibitors aka and what do they do

Irreversible Bind Supa tight to ACTIVE SITE forming covalent bond and permanently inactivate enzyme

Suicide inhibitors KM and VMAX effects

Vmax decreases KM is unchanged

Examples of suicide inhibitors

NSAID-Aspirin Penicillin

What kind of enzyme catalyzes irreversible metabolic reactions

Regulatory enzyme

Example of allosteric regulatory enzyme

Phosphofructokinase

Enzymes And RegulationOf Enzyems Flashcards

(69 cards)