Enzyme Regulation (Quiz 2) Flashcards
What are enzymes?
-proteins
-biological catalysts
-they accelerate specific chemical reactions
-some enzymes require molecules other than proteins for the enzymatic activity
What is a holoenzyme/haloenzyme?
-the active enzyme
-enzyme with nonprotein
-usually vitamins or minerals
-they’re essential for enzymatic activity
-ex: dehydrogenase with NAD
What is an apoenzyme?
-inactive enzyme
-its inactive bc it doesn’t have its nonprotein component, so if it gets its nonprotein component then it becomes activated and is now called a holoenzyme
-ex: dehydrogenase
What are cofactors?
-component of holoenzyme
-non-protein metal ion such as Cu, Mg, Zn
What are coenzymes?
-holoenzyme
-non-protein component is a vitamin (organic molecules)
-active form of vitamin
What are cosubstrates?
coenzymes that only transiently associate with the enzyme
What are prosthetic groups?
coenzyme (made of vitamin + protein) that is permanently associated with the enzyme
An active compound formed by a carboxylase + biocytin =
a holoenzyme
Which vitamin is associated with the coenzyme flavin adenine dinucleotide (FAD)?
riboflavin (vitamin B2)
Which vitamin is associated with the coenzyme nicotinamide adenine dinucleotide (NAD)?
nicotinic acid (also known as niacin or vitamin B3)
Which vitamin is associated with the coenzyme, Coenzyme A?
pantothenic acid, also known as pantothenate or vitamin B5
Which vitamin is associated with the coenzyme pyridoxal phosphate (PLP)?
pyridoxine (vitamin B6)
Which vitamin is associated with the coenzyme thiamine pyrophosphate (TPP)?
thiamin (vitamin B1)
Which vitamin is associated with the coenzyme biocytin?
biotin (vitamin B7)
Which vitamin is associated with the coenzyme tetrahydrofolate?
folic acid (vitamin B9)
Which enzymes are regulated?
only rate limiting enzymes
What are the 4 types of enzyme regulation mechanisms (cells don’t want to waste time and energy, so the enzyme needs to be regulated)?
1) allosteric regulation
2) covalent modification
3) activation by proteolytic cleavage
4) isozymes
In many pathways, the end product is an allosteric inhibitor of the first enzyme. This is called _________________ regulation
negative feedback
What is allosteric regulation?
-allosteric regulation binds to a site other than the active site and changes enzyme confirmation, which results in an apparent change in binding affinity
-the allosteric site that bonded will cause change in the active site so that the substrate cant bind to the active site
-its reversible binding of modulators to sites other than the active site
______ shape curve indicates a regulated enzyme
S
Does allosteric regulation have Km and Vmax?
no
Increased 2,3 BPG is an example of an allosteric __________
inhibitor
Presence of CO is an example of an allosteric _____________
activator
What is covalent modification?
-most common form of covalent modification is phosphorylation
-ser, thr, and tyr all have OH in their R group, so they can be phosphorylated (OH is replaced with phosphate)
-this is reversible and phosphate can go back to OH when needed
-hormones frequently do this, like insulin and glucagon to turn on and off enzymes
What is activation by proteolytic cleavage?
What are some examples of zymogens (type of inactive form of enzyme)?
What are isozymes?
-used for enzyme regulation
-groups of enzymes catalyze the same reaction but differ in AA sequence and enzyme properties
-example: Glut 1 and 2 are isozymes
What are the 6 classes of enzymes?
1) oxidoreductase
2) transferase
3) hydrolase
4) lyase
5) isomerase
6) ligase
Which enzymes are a part of the oxidoreductase enzyme class?
-oxidase (removes H/electrons)
-reductase (adds H/electrons)
-dehydrogenase (removes or adds H)
What type of reaction is catalyzed with oxidoreductase?
transfer of electrons or H atoms
Which enzymes are a part of the transferases enzyme class?
-kinase (adds phosphate)
-phosphorylase (breaks polymer and adds phosphate to one of the monomers)
-transferase
What type of reaction is catalyzed with transferases?
group transfer reactions
What 2 groups of enzymes are a part of the hydrolase enzyme class?
1) digestive enzymes
2) phosphatase (removes phosphate)
note: both use water in hydrolysis reaction to break bond
What type of reaction is catalyzed with hydrolases?
hydrolysis reactions (use water to break polymer into monomers)
Which enzymes are a part of the lyases enzyme class?
-decarboxylase (removes carbon)
-lyases
What type of reaction is catalyzed with lyases?
breaking of various chemical bonds by means other than hydrolysis and oxidation
Which enzymes are a part of the isomerases enzyme class?
-mutase (name is same)
-isomerase (isomers are molecules with the same formula but different structure)
What type of reaction is catalyzed by isomerases?
isomerization
Which enzymes are a part of the ligase enzyme class?
-synthase (ATP not seen directly in rxn)
-synthetase (ATP seen directly)
-carboxylase (adds carbon)
What do ligases do?
join 2 molecules with covalent bonds usually coupled with ATP hydrolysis
What does oxidase do?
removes H or electrons
What does reductase do?
adds H or electrons
What does dehydrogenase do?
removes or adds hydrogen
What do kinases do?
add phosphate
What does phosphorylase do?
breaks polymer and adds phosphate to one of the monomers
What does phosphatase do?
removes phosphate and uses water for hydrolysis reaction
What does decarboxylase do?
remove carbon
What do synthases do?
used in reactions without ATP directly present to glue molecules together
What do synthetases do?
used in reactions with ATP directly present to glue molecules together
The enzyme trypsin is classified as which of the following?
A) oxidoreductase
B) lyase
C) hydrolase
D) ligase
C) hydrolase
What does the inhibitor bind to during feedback inhibition?
allosteric site of the enzyme being inhibited
