Enzymes Flashcards
Enzymes enhance reaction _______ but do not change the ________.
Rates; Equilibrium
What is the name of the enzyme that is used as a monitor for liver and kidney disease? It is normally a cytoplasmic enzyme most abundant in liver and is released into the blood after liver damage.
Alanine amino transferase (ALT or ALAT)
Enzymes lower free energy of activation by stabilizing ______?
The transition state
What are transition state analogs?
Stable molecules that look similar to the transition state, often used to make drugs.
EX = allopurinol is used to inhibit xanthine oxidase to treat Gout
Binding of substrate by the enzyme increases the _____ of the substrate.
effective concentration
What are the two types of enzyme catalysis?
Acid-Base and covalent
What does an amylase do?
Breaks down carbohydrates
Digestive proteases are activated by?
Specific proteolytic cleavage
Proteolytic digestive enzymes are synthesized as inactive precursors (________) that are activated after secretion
zymogens
Is pancreatic lipase a zymogen?
No
Are trypsin and chymotrypsin zymogens?
Yes
What three amino acids make up the catalytic triad for proteolytic cleavage enzymes?
Asparate, Histidine, Serine
What proteolytic cleavage enzyme activates chymotrypsin?
serine protease
Reversible inhibitors interact with an enzyme via ______ associations while irreversible interact via _______ associations
noncovalent, covalent
What are the three types of reversible inhibitors?
Competitive, Noncompetitive, uncompetitive
A competitive inhibitor binds to?
The enzyme’s active site
A noncompetitive inhibitor binds to?
Either the enzyme or the enzyme substrate complex
An uncompetitive inhibitor binds only to?
The enzyme substrate complex
A competitive inhibitor ______ Km and _______ Vmax
Increases Km but does not change Vmax
What is the committed step for cholesterol synthesis?
The synthesis of mevalonate
What enzyme synthesizes mevalonate and in turn is necessary for cholesterol synthesis?
HMG-CoA reductase
What type of drugs are used to inhibit HMG-CoA reductase to decrease blood cholesterol?
Statins
What type of inhibitors are statins?
competitive - they are shaped like mevalonate
Nerve gas is what type of enzymatic inhibitor? what does it inhibit?
Irreversible
Acetylcholinesterase
What are muscarinic acetylcholine receptors?
Main G-protein receptor complex in neurons of the PNS
What activates muscarinic receptors of neurons?
Acetylcholine
What enzyme metabolizes acetylcholine?
Acetylcholinesterase
What happens if acetylcholinesterase is inhibited?
PNS problems, such as rigor mortis and paralysis
What is the antidote for acetylcholinesterase inhibitors like nerve gas and parathion?
Atropine, it blocks access to muscarinic receptors
Asprin is an irreversible inhibitor of what 2 enzymes?
COX-2 and COX-1
Why does Asprin cause stomach problems?
COX-1 which it inhibits, is essential for stomach health
What type of enzyme responds differently to different substrate concentrations?
Isozymes
What two isozymes phosphorylate glucose?
Hexokinase (RBC)
Glucokinase (Liver)
Which has a lower km hexokinase or glucokinase?
Hexokinase (RBC) has a low Km while glucokinase (liver) has a high Km. This ensures that RBCs get glucose when concentrations are low.
What do Kinases do?
Add phosphate
What do phosphatases do?
Removes phosphate
What three amino acids can be phosphorylated?
serine, threonine, tyrosine
What is the most common example of reversible covalent modification?
Phosphorylation/dephosphorylation of ser, thr, tyr
What is the regulated enzyme of fatty acid synthesis?
Acetyl CoA carboxylase
What is the end product of fatty acid synthesis and is also a feedback inhibitor of Acetyl CoA carboxylase?
Palmitoyl CoA
Do allosteric enzymes obey Michaelis-Menten Kinetics?
No
What does a allosteric enzyme substrate/reaction velocity curve look like?
Sigmoidal
What is a key trait of allosteric enzymes?
They display cooperativity - activity of one functional site affects the activity at other sites
What is Phosphofructokinase 1 (PFK1) activated by allosterically?
AMP
