Enzymes Flashcards
1
Q
enzyme definition
A
protein that catalyzes a biological reaction
2
Q
not altered or consumed during reaction
- reusable
- accelerate reactions
A
enzymes
3
Q
where are enzymes found?
A
in all body tissue
ex. heart attack = increased cardiac enzymes
4
Q
clinical benefit of enzymes
A
helpful in making diagnosis
5
Q
isoenzyme definition
A
enzymes that exist in multiple forms, but catalyze the same chemical reaction (same substrate)
6
Q
how to differentiate isoenzymes
A
electrophoretic mobility
differences in absorption properties
reactions with specific antibodies
7
Q
cofactor definition
A
non-protein molecules required for enzyme activation
8
Q
cofactor types
A
Activators, Coenzymes
9
Q
Common co-factor activators
A
Ca2+, Fe2+
10
Q
common coenzymes
A
ATP, ADP, NAD
11
Q
EDTA and calcium
A
some anticoagulants remove cofactors, EDTA removes calcium
12
Q
Holoenzyme definition
A
Functional unit consisting of apoenzyme and cofactor
13
Q
apoenzyme
A
protein portion of holoenzyme
14
Q
Proenzyme/zymogen
A
inactive enzyme that requires biomechanical change to become active
15
Q
Digestion enzymes
A
example of proenzyme
16
Q
Cavity where substrate interacts
A
active site
17
Q
site on enzyme where cofactors or regulatory molecules interact
A
allosteric site
18
Q
Inhibitor attaches at
A
allosteric site
19
Q
Basic enzyme reaction
A
S+E –> ES –> E+P
20
Q
describes the nature of the reaction
ex. 1,4-glucagon-4-gluconohydrolase (amylase)
A
Systemic name
21
Q
how do enzymes catalyze reactions?
A
lowering the activation rate
22
Q
working/practical name
ex. amylase
A
recommended name
23
Q
Numerical code
A
first digit = class second/third digit= subclass fourth digit=specific serial number
24
Q
Standard abbreviated name
A
accompanies recommended name
ex. AMS (amylase)
25
common abbreviated name
ex. AMY (amylase)
26
enzyme combines with only one substrate and catalyze one reaction
absolute specificity
27
enzymes combine with all substrates containing particular functional groups
ex. amino, phosphate, methyl groups
Group specificity
28
act upon certain chemical bonds
act upon certain chemical bonds
29
act upon specific stereoisomers of substrates.
| ex. Glucose oxidase acts on D-glucose
Stereoisomeric specificity
30
excess energy that raises all molecules at a certain temperature to the activation energy
-determines how fast a reaction will proceed
activation energy
31
influencing factors on enzymatic reactions
- substrate concentration
- enzyme concentration
- pH
- temperature
- cofactors
- inhibitors
32
pH and enzymatic reactions
7.0-8.0 pH
changes can denature enzyme
buffer systems used to control pH
33
Temperature and enzymatic reactions
37 degrees C
increasing temp increases rate of reaction
extreme low/high can denature enzyme
34
reaction velocity and temperature
doubles for each 10 degree increase until 50 degrees then denaturation occurs
35
any substance that competes with the substrate for the active/binding sites (reversible)
competitive inhibition
36
a substance that binds to an allosteric site instead of competing with substrate
noncompetitive inhibition
37
relationship of the reaction velocity/rate to the substrate concentration
Michaelis-Menten (Km) Curve
38
Km constant
the substrate concentration in moles/liter when initial velocity is 1/2 V max
39
first-order kinetics
enzyme concentration is fixed, substrate is varies
40
rate is directly proportional to substrate concentration
first-order kinetics
41
method for measuring substrate
glucose
42
zero-order kinetics
reaction rate depends on enzyme concentration
43
plateau is reaches: all enzyme bound to substrate
zero-order kinetics
44
method for measuring enzyme
LD
45
low Km =
low substrate needed
46
high Km
more substrate is needed
47
clinical enzymes
measure activity of enzymes in patient serum
| ex. LD, AST
48
substrate concentration should not be limiting factor (clinical enzymes)
need excess substrate and cofactors to handle possible abnormally high patient enzyme levels
49
if substrate and coenzyme are in excess, reaction rate is controlled by ENZYME
zero order kinetics in lab
50
measure amount of substrate in patient serum
analytical enzymes
51
glucose, cholesterol
analytical enzyme ex
52
analytical enzymes and kinetic order
first order kinetic
53
enzymes are not directly measured in lab
enzymes usually present in small quantities in bodily fluids, also difficult to isolate
54
how labs measure enzymes
-catalytic activity
55
enzymes activity can be tested by measuring
-increased product
-decreased substrate
-decreased coenzyme
-increased altered coenzyme
NAD+, NADH
56
leakage from cells (entry of enzymes)
damage to cell membrane
| virus/chemical injury
57
altered production of enzymes
increased synthesis
| increased osteoblastic activity
58
entry of enzymes into blood
leakage from cells
| altered production of enzymes
59
clearance of enzymes
half life varies
60
increased serum levels of enzymes
cell damage,death
increased production
impaired disposition (jaundice/renal failure)
61
decreased serum enzymes
decreased formation (genetic or acquired)
enzyme inhibitor
lack of cofactors
62
measuring enzyme activity
- single step reaction
ex. NAD++Lactate -LD--> pyruvate + NADH
-consecutive enzyme reactions
63
product of one reaction becomes substrate of another reaction
consecutive enzyme reactions
64
reaction is started and allowed to continue for a fixed period of time and the stopped. product is measured (enzyme activity)
fixed time
65
multiple measurements of absorbance changes are made (enzyme activity)
-decreased substrate concentration/increased product
continuous monitoring/kinetic
66
enzyme mass
measure protein mass NOT catalytic activity
| ex. CK-MD isoenzymes
67
clinical significance of enzyme testing
diagnosis of disease
68
International unit of enzyme activity
1 umol substrate/ minute
| IU/L
69
Kata unit of enzyme
1 mole substrate/ 1 second
70
Catalyzes transfer of phosphate between creatine and ATP
| -rapid regeneration and storage of ATP
Creatine Kinase
71
creatine kinase source
skeletal muscle
cardiac muscle
brain tissue
72
CK Isoenzymes
CK-MM
CK-MB
CK-BB
73
CK-MM location
striate muscle and serum
74
Increased CK-MM
Myocardial Infarction, Dystrophy, polymyositis, hypothyroidism, IM injections
75
CK-MB location
heart / skeletal muscle
76
increased CK-MB
Myocardial infarction, angina, ischemia, cardiac surgery
77
CK-BB location
brain, bladder, lung, prostate, uterus, colon, stomach, thyroid
78
increased CK-BB
CNS, shock, seizure, carcinoma, placental/urterine trauma
79
relative index equation
Relative index (RI)= (CK MB)/(total CK) X 100
80
relative index ref range
<3% - normal
| >6% = cardiac issue
81
Relationship between thyroid and CK
Hypothyroid: Increased CL
Hyperthyroid: Decreased CK
82
creatine kinase reference range
Male: 48-171 U/L
Female: 34-145 U/L
83
Creatine kinase specimen
serum
84
creatine kinase interferences
```
adenylate kinase (hemolysis) -> false elevation
CK is inactivated by light
```
85
Oliver and Rosalki
common CK assay
86
Lactate dehydrogenase (LD) source
- skeletal muscle
- cardiac muscle
- liver
- kidney
- RBCs
87
Catalyzes reversible reaction between pyruvate and lactate with NAD as a coenzyme
Lactate dehydrogenase
88
LD-1
Cardiac, RBCs
89
LD-2
Cardiac, RBCs
90
LD-3
lung, pancreas
91
LD-4
liver, kidney, placenta, pancreas
92
LD-5
liver and skeletal muscle
93
Healthy LD pattern
LD2>LD1>LD3>LD4>LD5
94
MI: Flipped LD
LD1>LD2>LD3>LD4>LD5
95
flipped LD pattern disease states
hematologic and neoplastic disorders
pernicious anemia
liver disease
heart prodlems
96
LD assay specimen
serum
| run asap and store at room temp
97
LD reference range
125-220 U/L
98
enzyme which reflect damage to hepatocytes
```
Aspartate aminotransferase (AST)
Alanine aminotransferase (ALT)
```
99
Enzymes which reflect cholestasis
Alkaline Phosphatase (ALP)
100
Elevated in nearly all hepatobiliary disorders
| high levels in biliary obstruction
Gamma-Glutamytransferase (GGT)
101
Involved in transfer of amino group between aspartate and alpha-keto acids
AST (SGOT)
102
enzyme elevated in acute hepatocellular disorders (ex. viral hepatitis, cirrhosis)
AST
103
cholestasis
blockage downstream of liver (ex. pancreas, duodenum)
104
Karmen method
couples reaction
malate dehydrogenase indicator
340 nm
105
Karmen method enzyme
AST
106
AST specimen
serum, heparin plasma
-centrifuged
stable at room temp 48 hrs
107
AST ref range
5-35 U/L
108
AST hemolysis
falsely elevates
| AST is 10-15X higher in RBCs than serum
109
transfers amino group from alanine to alpha-ketoglutarate to form glutamate nd pyruvate
ALT (SPGT)
110
sources of ALT
liver
kidney
heart
skeletal muscle
111
ALT specimen
serum/heparin plasma
| centrifuged
111
ALT specimen
serum/heparin plasma
| centrifuged
112
ALT reference range
7-45 U/L
113
ALT enzyme assay
coupled reaction
lactate dehydrogenase indicator
340 nm
114
AST>ALT
alcoholic liver issue
115
nonspecific enzyme that frees inorganic phosphate from organic phosphate monoester which results in production of alcohol
Alkaline Phosphatase (ALP)
116
Source of ALP
bone, liver, kidney, intestines, placenta, spleen
117
elevated in bone activity, and paget's disease
ALP
118
ALP and liver disease
obstructive: 3-10X ULN (upper limit of normal)
hepatocellular: <3X ULN
119
ALP and pregnancy
1.5X - 3X elevated
120
ALP specimen
serum/heparin plasma
121
ALP hemolysis
RBCs contain 6X more ALP than serum
122
ALP ref range
teens: 54-369 U/L
males: 53-128 U/L
old men: 56-119 U/L
Females: 42-98 U/L
Old women: 53-141 U/L
123
catalyzes phosphate esters, ph 5
Acid Phosphatase (ACP)
124
Aids in detection of prostatic carcinoma
prostate conditions
forensic chemistry (rape)
elevated in bone disease
ACP
125
ACP source
prostate, seminal fluid, bone, spleen, RBCs, platelets
126
ACP specimen
serum/hep plasma
127
ACP ref range (prostatic)
0-3.5 ng/mL
128
Possible involved in peptide and protein synthesis, transport of amino acids and regulation of tissue glutathione levels
Gamma-Glutamyltransferase (GGT)
129
GGT clinical signif
Indicator of liver damage
| differentiating increased ALP--> GGT is not elevated in bone disease
130
GGT specimen
serum/hep plasma
| very stable
131
GGT ref range
male: 6-55 U/L
female: 5-38 U/L
132
Hepatits elevated enzymes
AST
ALY
GGT
Bilirubin
133
Biliary obstruction elevated enzymes
ALP, GGT, Bilirubin
134
digestive enzyme that catalyzes breakdown of starch and glycogen to carbohydrates
Amylase (AMY)
135
AMY isoenzymes
P-AMY (pancreas)
| S-Amy (Salivary)
136
source of AMY
acinar cells of pancreas and salivary glands
137
AMY acute pancreatitis
2.55x ULN
138
AMY salivary gland lesions
mumps
| parotitis
139
increased amylase
peptic ulcer, appendicitis, cholecystitis, intestinal obstruction, ectopic pregnancy, macroamylsemia
140
macroamylasemia
artifactual increase in serum amylase level
- combines with immunoglobulins
- UA amy decrease (complex too large to pass glomerulus)
141
AMY assay
340 nm
Amyloclastic
Saccharogenic
Chromogenic
142
Amylase Creatinine Clearance Ratio (ACCR)
acute pancreatitis >8%
| macroamylasemia <2%
143
amylase specimen
serum/hep plasma/urine
144
amylase ref range
serum: 28-100 U/L
Urine: 1-15 U/h
145
amylase errors
opiates increase levels
| stabile
146
Hydrolyzes triglycerides to produce alcohols and fatty acids
Lipase (LPS)
147
LPS clinical sig
```
Acute pancreatitis (more specific than amylase)
normal in salivary glands
```
148
LPS assay
Cherry-Crandall
turbidimetry
550 nm
149
LPS specimen
serum/hep plasma
150
LPS ref range
<38 U/L
151
LPS hemolysis
false decrease
152
Acute pancreatitis
increased Amylase
| increased Lipase
153
Alolase
skeletal muscle diseases
154
cholinesterase
pesticide poisoning
| liver function test
155
G-6-PD
RBCs
glucose metabolism
hemolytic anemia
