enzymes Flashcards
(123 cards)
1
Q
Activation energy definition
A
the energy required to raise the temp of 1 mole of a compound to a transitional state
2
Q
transitional state is where…..
A
reaction can go backwards & forwards in equal amounts
E+S ES E+P (ES = transitional state)
3
Q
Enzyme active site is where…
A
substrate interacts with molecule
4
Q
Enzyme Allosteric site is …
A
part of the enzyme that does not interact with substrate
5
Q
Isoenzymes are…
A
different forms of the same enzyme
6
Q
Cofactors are:
A
A non-protein molecule required for the enzyme to function
7
Q
activators are:
A
Inorganic cofactors
ex. Mg or Cl
8
Q
Coenzymes are:
A
organic cofactors
ex. NAD+
9
Q
Functioning enzyme =
A
Apoenzyme + coenzyme
10
Q
Zymogen is:
A
inactive form of an enzyme
11
Q
Apoenzyme is:
A
enzyme portion of the molecule after coenzyme disconnected
12
Q
Why would a zymogen be released in the body?
A
To be activated elsewhere
13
Q
6 classes of enzymes
A
oxireductases transferases hydrolases lyases isomerases ligases
14
Q
Lyases work to…
A
remove substrate groups
15
Q
Isomerases work to…
A
catalyze the interconversion of isomers
16
Q
Ligases work to…
A
join 2 substances
*needs ATP
17
Q
Oxidoreductase enzymes (2)
A
LDH
G6PDH
18
Q
Transferases (4)
A
AST
ALT
CK
GGT
19
Q
Hydrolases (5)
A
ALKP ACP SAMY LIPA Cholinesterase
20
Q
First order kinetics Rxn used to measure ____
A
substrate
21
Q
First order: Rxn rate proportional to ______ concentration
A
substrate
22
Q
_____ in excess in 1st order kinetics
A
Enzyme
23
Q
Zero-order kinetics used to measure ____
A
enzyme
24
Q
____ in excess in zero order kinetics
A
substrate
25
zero order Rxn rate proportional to _____ conc.
enzyme
26
How is rate measured?
Michaelis-menton equation
27
curves are used to find ___ and ___ of M-M equation
Vmax
| Km
28
6 things that influence enzymatic reactions
```
Enzyme concentration
pH
temp
cofactors
coenzymes
inhibitors
```
29
Enzyme concentration;
If S>E, V is proportional to __
If E>S, V is ____
V
| Faster
30
Cofactors allow for: (3 things)
Substrate binding
Substrate linkage
Redox Rxns
31
Prosthetic groups
(coenzymes)
| Tightly bound second substrate
32
3 types of inhibitors
Competitive
Noncompetitive
Uncompetitive
33
competitive inhibitors
Substance that binds to active site of enzyme, competes with substrate
34
Noncompetitive inhibitor
binds to a site other than active site on enzymes and deactivates enzyme
35
Uncompetitive inhibitor
binds to enzyme-substrate complex
36
Indirect measurement of enzymes requires
auxiliary enzymes to visualize Rxn
Continuous readings
(usually done with zero-order kinetics)
37
International Units quantify...
enzymes based on activity (rather than direct measurement)
| Measured in IU/L
38
IU =
amount of enzyme required to catalyze the reaction of 1 umol of substrate per minute under specified conditions
39
Ways to directly measure enzymes (2)
immunoassays- attaching Ab to actual enzyme, measuring protein and quantifying amount present
Electrophoresis
40
CK =
Creatine kinase
41
CK fx
Storage of creatine phosphate in muscle cells
Helps form CP from Creatine (catalyzes Rxn)
Creatine + ATP to Creatine Phosphate + ADP
(Transferase)
42
Source of CK
Widespread distribution, incl skeletal muscle, heart muscle and brain tissue
43
Diagnostic significance of CK
Isoenzyme activity
AMI or muscle breakdown
CKMM, MB, MM
44
____ is used to indirectly quantitate CK
NADH--NAD+
45
CK interference
hemolysis (false elevation due to color)
46
CK reference ranges
Male: 60-380 U/L
Female: 40-195 U/L
47
Normal CKMB
<6% of total CK
48
LD =
lactate dehydrogenase
49
LD function
supports the interconversion of lactate to pyruvate
| oxidoreductase
50
LD tissue source
Nonspecific:
| Heart, liver, skeletal muscle, kidney, RBC
51
Diagnostic significance of LD
Hemolytic disorders
Liver disorders
Tumor markers
also: oncology- how well pt's RBCs withstanding Tx
52
LD 1 and 2
Heart, RBCs
53
LD-3
lung, lymphocytes, spleen, pancreas
54
LD-4
liver
55
LD-5
skeletal muscle
56
Stability of LD
More stable at RT than refrigerated, no more than 1 day
57
LD activity assay
Lactate + NAD+ to Pyruvate + NADH + H+
58
LD sources of error
hemolysis
| age of sample
59
LD reference range
135-225 U/L
60
AST =
Aspartate Aminotransferase
Also: SGOT or GOT
61
AST fx
transfers an amino group from aspartate and alpha-keto-glutarate
Transaminase reaction important in the breakdown and creation of amino acids
(transferase)
62
AST tissue source
heart
liver
skeletal muscle
63
AST diagnostic significance
Liver function
small increase in AMI and muscle disorders (not used for Dx)
64
AST sources of error
hemolysis (not affected as much as LD or CK)
| platelets (increase)
65
AST reference range
11-41 U/L at 37C
66
If AST and ALT both very elevated, indicative of...
hepatitis
67
If ALKP and GGT both every elevated, indicative of...
cirrhosis
| obstruction
68
Onset of cirrhosis, ___ will increase first
GGT
69
ALT =
alanine aminotransferase
also: SGPT, GPT
70
ALT fx
(transferase)
| transfers an amino group from alanine to alpha-keto-glutarate
71
ALT source
LIVER
72
ALT significance
Evaluation of hepatic disorders
73
ALT reference range at 37C
male: 11-66 U/L
female: 9-40 U/L
74
ALT interferences
slightly affected by hemolysis
| Quite stable
75
ALKP =
alkaline phosphatase
76
ALKP fx
catalyzes hydrolysis of phosphomonoesters at alkaline pH
| hydrolase
77
ALKP conditions
Optimal pH 9-10
| Requires Mg+ as an activator
78
ALKP source
Nonspecific
| intestine, liver, bone, spleen, placenta, kidney
79
Diagnostic significance
liver and bone diseases
80
Low levels of ALKP indicative of...
bone disorder in kids, nothing in adults
81
ALKP isoenzyme historical test:
heat to 56C for 10 minutes... Bone burns
<20% left = bone fraction
>20% left = lover fraction
82
ALKP sources of error
Hemolysis and secretor status (Blood type B or O and nonsecretor may have slightly low levels)
Will increase in activity after 24 hours
83
ALKP Reference range
32-110 U/L
| age dependent... may be up to 500-600 in kids
84
ACP =
acid phosphatase
85
ACP fx
(hydrolase)
catalyzes hydrolysis of phosphomonoesters at acid pH
(optimal pH = 5)
86
ACP tissue source
prostate, liver, bone, spleen, kidney, RBC, plts
87
ACP diagnostic significance
Prostatic ACP- esp when metastasized
(monitor prostate cancer)
Increased in bone diseases
can help ID semen
88
Way to differentiate prostatic ACP
Inhibited by tartrate
89
ACP sources of error
Immediate serum spin
90
ACP ref range
0 - 3.5 ng/mL
91
GGT =
gamma-glutamyltransferase
92
GGT fx
involved in peptide and protein synthesis (transferase)
transfers gamma-glutamyl from peptides to amino acids, water, and other small peptides
93
GGT source
kidney, brain, prostate, pancreas, liver
94
GGT diagnostic significance
LIVER disease
high results in biliary tract obstruction
alcoholism
drugs- warfarin, phonobarb, phenytoin
95
GGT sources of error
Usually stable
96
GGT ref ranges
male: 8-100 IU/L
female: 5-40 IU/L
97
Amylase fx
breaks down starch and glycogen
98
Amylase requires
Calcium and chloride
99
Amylase tissue source
Acinar cells of the pancreas and salivary glands
100
Amylase isoenzymes
```
S-amy = salivary
P-amy = pancreatic
```
(S + P = total amy)
101
Amylase diagnostic significance
```
acute pancreatitis
salivary dysfunction (mumps)
```
102
Is amylase affected by hemolysis?
no
103
4 assays for amylase
Amyloclastic (use of iodine)
Saccharogenic (amt of reduced sugars)
Chromogenic (dye-substrate)
Coupled enzyme (NAD+ measurement)
104
Amylase reference range
30-105 IU/L
105
Lipase fx
breaks down fats to alcohols and fatty acids
| hydrolase
106
lipase tissue source
pancreas
| more specific than AMY
107
lipase diagnostic significance
acute pancreatitis
108
Lipase source of error
hemolysis (not much)
109
Lipase ref range
15-100 IU/L
110
G6PD (G6PDH) =
Glucose-6-phosphate dehydrogenase
111
G6PD fx
(oxidoreductase)
oxidation of glucose-6-phosphate to 6-phosphogluconate
Important in the first step of glucose metabolism leading to NADPH production
112
G6PD source
Adrenal cortex, spleen, thymus, lymph nodes, lactating mammary gland, RBCs
113
G6PD diagnostic significance
Decreased levels: sex-linked deficiency, usually in African Americans (oxidative drugs can cause hemolytic episode)
Increased: MI, megaloblastic anemia
114
G6PD and RBCs
protects hgb from oxidation and thus hemolysis
115
G6PD assay rxn
NADPH production
116
Neuron-specific enolase found in
neurons and neuroendocrine cells
117
neuron-specific esterase test used for...
tumors of neuroendocrine system:
neuroblastoma
small cell carcinoma of the lungs
islet tumor cells
118
5'-nucleotidase elevated in...
bile duct obstruction (highest increase)
| hepatitis (moderate increase)
119
5'-nucleotidase used in conjunction with ___
ALKP
120
cholinesterase found in:
RBC, lungs, spleen, nerve endings and brain
121
cholinesterase, 2 similar enzymes:
acetylcholinesterase
| acylcholine acylhydrolase
122
Cholinesterase used for:
liver fx
insecticide poisoning
detect atypical form of enzyme for surgery (anesthesia- if pt has less active forms may not wake up when under)
123
Cholinesterase fx
degrades acetylcholine, depolarizes nerve so another signal can send (hydrolase)
