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Enzyme Kinetics

Terms in this set (41)

Kd
dissociation constant that accounts for amount of reactant that dissociates reversibly to form component products
kcat
turnover number (molecules catalyzed per second in optimal conditions)
Vmax / [E]
Km
concentration of substrate which permits the enzyme to achieve half Vmax
Vmax
rate of reaction when the enzyme is saturated with substrate
small kd
high affinity
-smaller concentration of substrate required to saturate 50% of the enzyme available
Kcat/ Km
catalytic efficiency
Hill coefficient
A measure of cooperative interaction between protein subunits
n greater than 1
cooperativity
n=1
no cooperativity
n less than 1
negative cooperativity
negative cooperativity
first binding event reduces affinity at remaining sites
kd formula
[Enzyme][Substrate]/[Enzyme-Substrate].
Ka
association constant for the binding reaction, and is a measure for the affinity of an enzyme for its substrate
kcat formula
Vmax/[E]total
Competitive inhibition
-km and kd increase
-vmax unchanged
----DOES NOT AFFECT ENZYME ITSELF
-crosses at Y axis
noncompetitive inhibition
-vmax decreases
-km and kd unchanged
uncompetitive inhibition
all decrease
-bound to the ES complex
-parallel lines
mixed inhibition
The inhibitor can bind either the naked enzyme or the ES complex
-vmax decreases
-km and kd either increase or decrease
Native electrophoresis
proteins are in their native state, not denatured
• no detergent
• proteins migrate through the gel based on physical
properties of:
-size
-charge
SDS PAGE
denatures the proteins and masks the native charge so that comparison of size is more accurate, but the functional protein cannot be recaptured from the gel
Reducing SDS-PAGE
Exactly the same as SDS-PAGE, but with the addition of a reducing agent, b-mercaptoethanol, which will reduce the disulfide bridges and result in a completely denatured protein.
cofactors vs coenzymes
A cofactor is a non-protein chemical compound. "helper molecule".
Coenzymes are cofactors that are bound to an enzyme loosely. A coenzyme is a small, organic non-protein molecule. It carries chemical groups between enzymes.
Michaelis-Menten equation
Michaelis-Menten graph
Covalently modified enzymes
enzymes can be activated or deactivated by phosphorylation or dephosphorylation

Can also be modified by covalent attachment of sugar groups (glycosylation)
missense mutation
A base-pair substitution that results in a codon that codes for a different amino acid.
nonsense mutation
A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein.
stop codons
UAA, UAG, UGA
small nuclear ribonucleoproteins
remove introns and splice exons together
small nuclear RNAs
help process pre-mRNAs into mRNAs
eukaryotic ribosome
60S + 40S = 80S
prokaryotic ribosome
50S + 30S = 70S
Post-translational modification of proteins
the covalent and generally enzymatic modification of proteins following protein biosynthesis
-phosphorylation
Repetitive DNA
noncoding DNA present in multiple copies in the genome
Jacob-Monod Model
DNA binding proteins
stabilize the single-stranded DNA & keep the strands apart
DNA acetylation vs. methylation
-acetylation occurs at lysine residues (neutralizes charge) and it increases gene expression in general
-methylation increases + charge and prevents transcription
southern blot
DNA sample, DNA probe
northern blot
involves radioactive DNA probe binding to sample RNA
western blot
sample is protein, probe is antibody
Hardy-Weinberg equilibrium
condition that occurs when the frequency of alleles in a particular gene pool remain constant over time
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