Chapter 19: Enzymes

What is an enzyme?

biomolecule that catalyze biological reactions

What is the reactant called in an enzyme-catalyzed reaction?

substrate

Structures

Look at notes

In most cases, what does the name of an enzyme end in?

“ase”

The enzyme is named by the substrate it binds to AND?

the type of reaction catalyzed

Special Cases for enzyme names?

they are historical

3 types of digestive enzymes

trypsin

chymotrypsin

pepsin

3 Types of Hydrolysis reactions

Proteases (break peptide bond)

Lipases (break ester bond)

Lactases (break glycosidic bond)

What is the substrate in protease/peptidases reaction

protein or peptide

What is the substrate in lipases reactions?

lipids

What is the substrate in lactases reactions?

carbohydrates

What are the 6 general classes of Enzymes

1) Oxidoreductases

2) Transferases

3)Hydrolases

4) Lyases

5) Ismoerases

6) Ligases

What is the reaction type and examples of oxidoreductases

Reduction; dehydrogenases, oxidases

What is the reaction type and examples of transferases?

Transfer a functional group; kinases (transfer of phosphoryl group)

What is the reaction type and examples of hydrolases?

hydrolysis; proteases, lipases

What is the reaction type and examples of Lyases?

add or remove a group from a double bond (make or remove); decarboxylases

What is the reaction type and examples of isomerases?

isomerization; mutases

What is the reaction type and examples of ligases?

make or break a bond; carboxylases

What is the equilibrium constants?

difference in energy between reactants and products

How does an enzyme affect the equilibrium contant?

it does not affect it

How does the enzyme catalyzed reaction affect the activation energy?

lowers it form a normal one but speeds up the rate of the reaction

What is the 1st stage of an enzyme catalyzed reaction?

it is the formation of the enzyme-substrate complex

what is the 2nd stage of an enzyme catalyzed reaction?

it is the conversion of substrate into product

what is the active site?

location on enzyme that binds the substrates

what is the lock and key model?

rigid and perfectly complentary

what is the induced?

flexible, not as strict but still complementary

Enzyme Specificty

ability of an enzyme to bind only 1 or a few structurally similar substrates

4 General types of specificity

1) Absolute

2) Group Specifitcy

3) Linkage specificity

4)Stereochemical specificity

What is absolute specificity?

enzyme can only bind to one substrate

what is group specificity?

can bind similar molecules (with similar structures/functional groups)

what is Linkage Specificity?

enzyme that catalyzes the reaction will either “make” or “break” the same type of bond

what is stereochemical specificity?

enzyme can recognize stereochemical differences (D vs. L)

what is the transition state?

substrate is in an intermediate form (features of both the substrate and the product)

What are the 3 types of transition state changes?

1) conformational change

2) proper proximity and orientation

3) Enzyme can modify its minoenvironment

What is conformational change?

enzyme puts “stress” on the substrate

What is proper proximity and orientation?

substrate is bound in a correct location (in active site) for catalysis to occur

What 2 things can enzymes bind?

cofactors and/or coenzymes

What are cofactors/coenzymes

a compound or molecule that binds directly to an enzyme and is necessary for it’s function (for the ability to catalyze) NOT A SUBSTRATE

What is an apoenzyme?

just the enzyme, no interactions, inactive (no substrate, coenzyme, or cofactors)

What is a holoenzyme?

The active site can be altered to allow for bonding of the cofactor and the substance (active)

What are the 3 types of regulation of enzyme activity?

1) Allesteric regulation

2) proenzyme/zymagens

3) Protein modification

what is Allesteric regulation?

molecule binds to the enzyme (not at the active site) that can either increase or decease the rate of a reaction

what is Proenzyme/zymagens?

in active enzyme precursor (digestive enzymes: go through a hydrolysis reaction to remove a peptide fragment to make the active form of the enzyme)

what is protein modification?

chemical change of an amino acids R group (phosphorylation/dephosphorylation)

What are the 2 environmental effects on enzymes?

1) pH optimum

2) Temperature optimum

What are the 2 types of inhibition of enzyme activity?

1) Irreversible inhibition: covalently binds to active site

2) Reversible inhibition: molecule can bind but also get released (Competitive inhibition)

What are proteolytic enzymes?

proteases or peptides (digestive)

What is protein hydrolysis?

break a covalent bond with addition of water

what is protein denaturation?

loss of organized structure (unfolding of 2, 3, and sometimes 4 structures)

How many nonpolar amino acids are there and which ones are they?

9

Glycine, alanine, valine, leucine, isoleucine, phenylalanine, proline, tryptophan, methionine

how many polar neutral amino acids are there and which ones are they?

6

Serine, threonine, tyrosine, cysteine, asparagine, glutamine

How many polar negatively charged amino acids and which ones are they?

2

Aspartate and Glutamate

How many polar positively charged amino acids and which ones are they?

3

Histidine, Arginine, lysine