Amino Acids, Proteins, & Enzymes Flashcards
imino acid
proline is considered this because of the NH2+ group instead of NH3
STCNQY
amino acids with polar side chains
DE
amino acids with negatively charged (acidic) side chains
RKH
amino acids with positively charged (basic) side chains
GAVLIMP
amino acids that are nonpolar with nonaromatic side chains
FWY
amino acids with aromatic side chains
phenylalanine, tyrosine
amino acids that are essential for production of dopamine, norepinephrine, epinephrine, thryoxine, melanin
tryptophan
amino acid that is essential for production of serotonin, melatonin, and vitamin b3 (niacin)
**high yield
histidine
amino acid essential for production of histamine
primary structure
amino acids linked together by peptide bonds, read from N to C terminus
secondary structure
alpha helix, beta sheet
cysteine
amino acid that forms disulfide bonds
glycine
amino acid with smallest side chain, often found at bends in protein structure
proline
amino acid with cyclic structure that causes a kink, often found in the bends of protein structure
denaturation agents
SDS, extreme pH, high temperature
Vmax
maximum rate of reaction possible, only way to increase it is to increase enzyme concentration
1/2 Vmax
Substrate concentration at this point on Michaelis-Menten graph is the Km
Km
michaelis constant, used to compare enzyme affinities. Lower affinity means higher this
1/Vmax
y-intercept of Lineweaver-Burk plot
-1/Km
x-intercept of Lineweaver-Burk plot
antabuse
example of irreversible enzyme inhibitor, this is an inhibitor of alcohol dehydrogenase - makes you hold onto acetaldehyde which causes prolonged and exacerbated hangovers - used to treat alcohol addiction
reversible inhibitors
most common type of enzyme inhibitors used clinically, can be competitive, noncompetitive, or uncompetitive
competitive inhibition
inhibitor binds to enzyme at active site, preventing substrate from binding. E + I = EI. No ES complex forms.
- increasing [S] overcomes this type of inhibition
- *This type of inhibition increases Km (decreases affinity), Vmax unchanged
noncompetitive inhibition
inhibitor binds to enzyme at site other than active site, forming EI complex. Substrate may still bind, forming EIS, but reaction cannot proceed to products.
- increasing [S] cannot overcome inhibition.
- *This type of inhibition does not change Km (affinity unchanged), but decreases Vmax.
uncompetitive inhibition
inhibitor binds ES complex (not at active site), EIS forms and reaction cannot proceed to products.
- increasing [S] will make the inhibition more effective.
- *This type of inhibition decreases both Km and Vmax
The apparent Km decreases because by binding to the enzyme-substrate complex, the inhibitors are “pulling” that complex out from the reactions. This removal of substrate decreases its concentration, and allows the remaining enzyme to work better.
sulfa drugs
example of using competitive inhibitor clinically for infection, this inhibits PABA and blocks bacterial production of folic acid
cyanide poisoning
example of using noncompetitive inhibitor - give the patient hydroxocobalamin to turn the poison into a nontoxic substance in the body
allosteric enzyme
enzyme with multiple active sites that allow for multiple types of regulation
- usually has multiple subunits with quaternary structure and multiple active sites
- Vo vs [S] plots give sigmoidal curve instead of hyperbola
- modulators of these enzymes bind to sites other than the active sites
- end products can be feedback activators or inhibitors
isoenzymes
enzymes routinely measured in blood samples, tissue-specific isoforms show where cellular damage is occuring in the body. Ex: troponin - heart, CK1 - brain, CK2 - heart, CK3 - skeletal muscle, AST and ALT - heart and liver.
high fever, drugs, sepsis
clinical conditions that can result in protein denaturation
