enzyme kinetics Flashcards
(124 cards)
1
Q
enzymes are
A
catalysts
-needed for every metabolic rxn in body
-NOT used up
-body temp
2
Q
enzyme’s are proteins which mean
A
-can be denatured
-complex in make up
-specific amino acid sequence
3
Q
substrate
A
substance upon which the enzyme will act
4
Q
active site
A
actual site where enzyme and substrate bind
may be charged
should fit in lock in key formation
5
Q
allosteric site
A
site other than the active site where other substances can bind to the enzyme, alternating the effects of it
6
Q
cofactor
A
non protein helper
-may be needed for reaction to occur
-organic or inorganic
7
Q
if cofactor is inorganic
A
referred to as activators
8
Q
if cofactor is organic
A
coenzymes
9
Q
coenzymes are compounds that are derivatives
A
from vitamin B or derivatives of NAD
10
Q
apoenzyme
A
has cofactor attached to it and is the enzyme part
11
Q
apoenzyme + cofactor
A
holoenzyme
12
Q
oxidoreductase
A
catalyzes oxidation-reduction reaction
13
Q
transferases
A
catalyzes the transfer of the group from one substrate to another
14
Q
hydrolases
A
cleaving of chemical bond by hydrolysis
15
Q
lyases
A
cleaving chemical bond without hydrolysis
forms double bonds
16
Q
isomerases
A
spatial configurations
17
Q
ligases
A
joining of 2 substrate molecules by forming a new covalent bond
18
Q
for enzyme to be formed need
A
activation energy
19
Q
activation energy
A
what is needed to remove the barriers that would prevent the product to be formed
20
Q
main role of enzyme
A
lowering energy for activation
21
Q
when 2 molecules come together they form
A
transitional unit (not a stable component) can move left or right; break down or form new product
22
Q
enzymatic reaction amount of product depends on the amount of
A
product the enzyme needs to act on upon
23
Q
enzymes found in what form in the body
A
free
-normally we look for increases
24
Q
only time we look for decreases in enzymes is
A
aminoacidopathy
25
absolute specificity
only act with one substrate
26
group specificity
only bind with specific group
27
bond specificity
only bind to certain kinds of bonds
28
we measure what of the enzyme
activity
-not directly
activity proportional to amount of enzyme present
29
activity of enzyme related to rate of
how fast it catalyzes rxn
(also proportional to amount of enzyme)
30
direct concentration of enzyme
very small- hard to measure
31
activity of enzyme only depends on
amount of enzyme present; not amount of substrate
32
factors that influence enzymatic reaction
substrate con
-will bind to enzyme only as long as enough substrate
33
idea of more enzyme than substrate
first order kinetics
34
in first order kinetics never fully reach
vmax= maximum velocity activity of an enzyme
35
substrate will always be excess of enzyme
zero order kinetics
-only rate limiting factor is enzyme
-recah vmax
-all enzymatic rxns performed at this
36
michaelis menten graph measures
concentration against the rate
37
as you add substrate the relationship between rate and con until you reach 1/2 vmax is
linear straight line
38
after 1/2 vmax as we add substrate the line becomes
hyperbola
39
vmax proportional to amount of
enzyme present
40
recognize the equation
go to notes
41
reference number to determine the right amount of substrate to ensure zero order kinetics
Km constant
42
what is substrate concentration
20 -100 times the Km value
43
Km values
between 10^-5 to 10^-3 mols/ L
44
Michaelis menton equation rearranged mathematically to be able to figure out Km values
Lineweaver-Burk plot
45
factors that influence enzymatic reactions
pH
temp
cofactor
46
in the body optimal pH
7
-changes in pH can denature enzymes
47
how do we control pH
buffer
48
what temp do rxns happen best at
35-37 degrees
-first thing that disrupts enzymatic rxn
49
cold temp will cause
slower movement of rxns
-may not reach maximum activity
50
lowering the temp can render
the enzyme reversibly inactive
- if not going to run immediately= refrige
freezing and thaw will denature
51
every 10 degrees increase in temp will
double rate of rxn
52
largest cofactor
magnesium
-if low Mg will affect rxns
53
competitive inhibition
compete with substrate for enzyme
-vmax can still be reached if enough substrate
-Km typ. higher
-no destroying
54
how to reverse competitive inhibition?
add more substrate
55
noncompetitive inhibitor
bind to allosteric site
-vmax will not be reached if active site is changed
-changing km will not have an effect
change formation of enzyme by pH
56
in noncompetitive inhibitor will adding more substrate make a difference?
no
57
uncompetitive inhibitor
bind to transitional site
-no product
-no vmax
more substrate= more transitional product
58
uncompetitive inhibitor will increasing substrate do
make it worse
59
how to measure enzymes
zero order kinetics
-activity in bell shaped curve
60
what period gets measured
log period
-add more substrate, enzyme activity increases
61
period called when first adding enzyme and substrate
lag period
-good time to measure
62
plateau
adding more substrate does not affect it
63
down side
substrate depletion phase
64
how can activity be measured
fixed time rxns
kinetic assay
65
fixed time
1 time assessment
-incubate the sample with substrate for a fixed time
66
kinetic assay
continuous monitoring
-measurements at different times (2 or more)
67
Enzyme measurements look for change in absorbance or conversion of
NAD ---> NADH or NADPH
68
when does NAD/NADPH has greater absorbance than NAD
340 nm
69
what do we measure at 340 nm
conversion of NAD ---> NADH or NADPH
70
what units are enzymes reported in
IU- international unit
-amount of enzyme that will catalyze the conversion of 1 mmol of substrate to product in 1 min
71
G6PD is
inherited deficiency
72
where is g6PD found
when clinically significant RBC's
-most common RBC enzyme deficiency
-when missing oxidizing agents
73
g6PD catalyzes the initial reaction of
pentose-phosphate shunt
74
oxidation of RBC membrane can lead to
heinz bodies
-need normal levels of Mg
75
what gender is G6PD more seen in
males
on X chromosome
76
causes of hemolytic anemia for G6PD
fava beans
moth balls (napthalene)
malaria medication
nitrofurantoin
tylenol
peanuts
peas
-more seen in black and oriental people
77
AST main concentration in
liver and cardiac tissue
-transferase enzyme
NO HEMOLYSIS
78
when is AST increased
liver
acute MI
pulmonary embolism
79
when is AST decreased
chronic hepatitis??
80
sister enzymes
AST
ALT
81
ALT is what enzyme
liver
anything liver makes will be affected when damage to liver
82
increases in ALT
Acute viral hepatitis and acute ischemic liver injury
83
where is GGT found
liver
indicator of alc cirrhosis
if increased need to look at alc levels
osmol gap >10
84
GGT also increased in
biliary obstruction
-more increase than ALT and AST
85
what enzyme inducing drug that causes increase in GGT that is not related to alc
warfarin
86
ALP highest con in
intestine, liver, bone
-osteoblasts
87
when is ALP increased
bili obsruction
multiple myeloma
bone cancer
3rd trimester
rickets
pagets
88
ALP isoenzyme made during preg
reagan
-if found when no preg, indication of germ cell cancer
89
how to tell difference between bone isoenzyme and liver iso
heat inactivation
measure total ALP
heat serum
remeasure
-bone will not be found bc heat labile
-liver found
90
amylase is the break down of
starch
91
when is amylase increased
acute pancreatitis
mumps
92
amylase is filtered in
urine and disappears quickly
93
what is the best indicator for pancreatitis
lipase
-stays longer
94
nonspecific seen in autoimmune disease
macromylasemia
-amylase hooks up to IG-- too big for urine
95
amylase specimen
NO LIPEMIA
false -
inhibits amylase activity
96
where is CK found
skeletal, heart, brain
main:
CK-MM
CK-MB
CK-BB
97
first enzyme increased after MI
CK
98
only fraction seen for CK in electrophoresis
CK-MM
-near cathode
99
what glycolysis for LDH
anaerobic
pyruvate to lactate (reduction of NADH to NAD)
100
how many isoenzymes for LDH
5
in normal serum LD-2 is higher than LD-1
101
in MI what happens to LDH isoenzymes
flipped ratio, LD-1 is higher than LD-2
102
last enzyme to increase in MI
LDH
1-CK
2-AST
3-LDH
103
in pernicious anemia LDH
increased
LD-1 highest
104
what LDH fraction highest in liver function
5
105
acid phosphate main source is found in
prostate
-hydrolase enzyme
106
acid phosphate tumor marker for
prostate cancer
-doesn't get that high until tumor metastases (not good early indicator)
-breast cancer
107
where is acid phosphatase used
forensic as evidence of rape
not found in vaginal fluid
place on ice, levels will decrease quickly
108
lipase enzyme breaks down
emulsified trigs
109
where is lipase found
pancreatic juices
-used for pancreatitis
110
why is lipase better than amylase
doesn't get lost in the urine
-stays in serum much longer
111
what inhibits activity of lipase
Hgb
112
amylase + and lipase -
need to think something else besides pancreatitis
113
streptokinase produced by
beta strep group A
-we can produce enzyme against beta strep group A
114
where is streptokinase increased
beta A glomerulonephritis
115
where is streptokinase used
therapy to help dissolve clots
-pulmonary embolism and coronary artery thrombosis
-can develop antibodies to it or develop (render therapy ineffective)
116
streptokinase also known as
plasminogen activating factor
plasmin cleaves fibrinogen and fibrin leading to formation of FDP
-watch carefully can bleed out
117
what does streptokinase increase and decrease
PT, PTT, FDP increased
fibrinogen and fibrin decreased
118
why is streptokinase different from heparin
in heparin we don't produce antibodies against
119
what does Pseudocholinesterase help with
nerve transmission
-look more for a deficiency than increase
120
what is Pseudocholinesterase issued with
succinylcholine
-people with deficiencies will not clear drug fast and have prolonged respiratory paralysis (ventilator)
121
deficiencies in Pseudocholinesterase are
inherited normally
or can happen when exposure to insecticide poisoning
122
indication of liver disease, but not commonly used
5' Nucleotidase
-highest elevation in obstruction
123
rises before ALP in cases of obstruction-- early indicator
5' Nucleotidase
124
5' Nucleotidase tumor marker for
liver cancer
-early stages
catching earlier is better
