Biochem Enzymes As Catalysts

Front 1

19th century ____ suggested that fermentation was catalyzed by "ferments"

Back 1

Louis Pasteur

Front 2

1878, _____ first used the term enzymes

Back 2

Wilhelm Kuhne

Front 3

1897, _____ found that sugar was fermented even with no living yeast cells

Back 3

Eduard Buchner

Front 4

1926, _____ showed that enzymes urease was a pure protein and crystallized it

Back 4

James B. Sumner

Front 5

Enzymes are _____

Back 5

protein catalysts

Front 6

Some types of ____ can act like enzymes called ____. Can cause cleavage or synthesis of phosphodiester bonds

Back 6

RNA

Ribozymes

Front 7

Each enzyme is assigned two names. Recommended name is convenient for everyday use. Suffix ____ attached to the ____ of the reaction. Or ______. Some enzyme names are trivial (ex. trypsin)

Back 7

-ase

-substrate (ex. urease)

-description of action (ex. alcohol dehyrogenase)

Front 8

Simple enzymes contain ____ only

Back 8

protein

Front 9

Complex enzymes are called _____. Protein component is called _____ and the non protein component are _____, which can either be loosely bound (____) or tightly bound (_____)

Back 9

holoenzymes

apoenzymes

cofactors

coenzymes

prosthetic group

Front 10

Many coenzymes are derivatives of _____

Back 10

vitamins

Front 11

Compartmentalization of enzymes inside cell serves to - (3)

Back 11

isolate the reaction, substrate, or product

provide favorable environment

organize enzymes into purposeful pathways

Front 12

____ are examples of secreted enzymes (2)

Back 12

digestive enzymes and blood coagulation enzymes

Front 13

____ are different enzymes that catalyze same reaction. They are usually located in (same/different) tissues or cellular organelles

Back 13

isozymes

different

Examples: HMG-CoA reductase, hexokinase and glucokinase

Front 14

_____ are expressed as inactive precursors that can then be activated by cleavage of extra sequence of protein

Back 14

Proenzymes

Examples: digestive proteases, enzymes in blood coagulation cascade

Front 15

Enzyme - catalyzed reactions have three basic steps:

Back 15

Binding (substrate to enzyme)

Conversion (substrate to product)

Release (product from enzyme)

Front 16

Enzyme has an active binding site that binds substrate (ES complex). Side chains and cofactors directly participate in reaction. E and S form state complex ____ which is ____, which then decomposes products from E

Back 16

TSC

Unstable high-energy complex

Front 17

Binding site determines enzyme ___

Back 17

specificity

Front 18

Substrate binding can occur through (3)

Back 18

hydrophobic, electrostatic, hydrogen bonds

Front 19

Two models for substrate binding

Back 19

lock-and-key and induced fit

Front 20

True/false - Enzymes are highly specific

Back 20

True

Glucokinase can bind to glucose, but not galactose, despite them being very similar

Front 21

Multiple interactions between the S and E involved in (2)

Back 21

Substrate recognition

Formation of transition state complex

Front 22

____ separates reactants and products. Enzymes lower ____ and do not change free energy of reactants and products

Back 22

energy barrier (barrier is free energy activation)

energy of activation

Front 23

Cofactors that participate in catalytic process include one of the following

-side chains of polypeptide
-functional groups of AAs
-coenzymes
-peptide bond

Back 23

coenzymes (can also be prosthetic groups)

Front 24

Explain the catalytic mechanism of chymotrypsin. Without enzyme, reaction is slow because too few -OH in H2O and too few -OH colliding in right orientation. Its faster with catalyst because (3). Reaction occurs in two stages:

Back 24

-OH from H2O attacks carbonyl carbon and H+ is added to N, cleaving the bond

Stabilize TSC, form covalent intermediate, destabilize the leaving group

Cleavage of peptide bond in denatured protein and formation of acyl-enzyme intermediate
Hydrolysis of acyl-enzyme intermediate to release remaining portion of substrate

Front 25

In catalytic mechanism of chymotrypsin, why must protein be denatured?

Back 25

to fit the pocket - active site

Front 26

Chymotrypsin hydrolyses peptide bond on the carbon side of _____

Back 26

Phe, Tyr, Trp (all aromatic)

Front 27

The _______ (D-H-S) - _____ located on active side of hydrolytic enzymes. Cooperate in interaction between _____ in active sites

Back 27

aspartate - histidine - serine

catalytic triad

AAs

Front 28

Functional groups that involve in catalytic reactions can be _____ in the case of ____ or _____ in the case of ______

Back 28

Serine - Serine proteases

Aspartate - Gastric protease pepsin

Front 29

In humans, coenzymes are usually from ____. Can either be ____ or ____

Back 29

vitamins

Functional - inhibition of coenzyme synthesis/failure to transport system

Dietary - inadequate intake

Front 30

Two-classes of coeznymes:

Back 30

Active-transfer coenzymes - form covalent bond with substrate

Oxidation-reduction coenzymes - do not form covalent bond with substrate (they donate or accept electrons)

Front 31

Example of oxidation-reduction coenzyme is when ______ catalyzes oxidation of ethanol. It is active as a ____, active site contains ____, along with ___ and ____. Coenzyme NAD+ is _____ during oxidation. _____ is a product of ethanol oxidation

Back 31

Alcohol dehydrogenase

dimer

Zn2+ - Ser - His

reduced

Acetaldehyde (highly reactive and toxic/responsible for liver disease)

Front 32

Metal ions can assist in catalysts by accepting or donating _____. Mg2+ is involved in binding of ______ of conezymes to enzyme

Back 32

electrons

phosphate groups

Front 33

ATP is usually bound to enzyme through ____

Back 33

Mg2+

Front 34

All nucleotides and enzymes involving nucleotide metabolism only work in the presence of ____

Back 34

Mg2+

Front 35

Different enzymes show different responses to changes in ____ and ___

Back 35

temperature and pH

Front 36

____ are compounds that decrease the rate of enzymatic reaction

Back 36

Inhibitors

Front 37

_______-based inhibitors mimic or participate in intermediate step of reaction

Back 37

Mechanism

Front 38

_____ inhibitors form covalent bond with functional groups in catalytic site. Examples - Organophosphorus toxins (Sarin) form covalent bonds with ___. _____ covalent acetylation of COX involved in prostaglandin synthesis

Back 38

Covalent

acetylcholinesterase

Aspirin

Front 39

_____ bind more tightly than substrate or product. Examples: _____ binds tightly to glycopeptidyl transferase that required for cell wall synthesis. ____ is suicide inhibitor of xanthine oxidase (to decrease urate production) used for treatment of gout

Back 39

Transition state analogous

Penicillin

Allopurinol

Front 40

_____ is caused by tight binding of metals to functional group. They are nonspecific and highdose

Back 40

Heavy metal toxicity

Front 41

4 metals that can cause heavy metal toxicity:

Back 41

Mercury (Hg) - often binds to SH- group of many enzymes

Lead (Pb) - inhibits by replacing normal functional metal in the enzyme (replacement of Ca2+ in calmodulin and protein kinase C)

Aluminum (Al) - interferes with iron transport and can cause anemia

Iron (Fe)