ENZYMES IN MEDICINE
• Diagnostic indicators – the activities of many enzymes are
routinely determined in plasma ( rarely in tissue biopsies) for
diagnostic purposes in diseases of the heart, liver, skeletal muscle,
pancreas and other tissues - enzyme diagnostics
• Therapeutic agents – several enzymes are used as drugs; new
approach - enzymotherapy
•
Diagnostic tools – use as chemicals in clinical laboratory assays
ENZYMES IN CLINICAL DIAGNOSIS
secretory - produced by tissues (namely
liver), acting in plasma –
prothrombin, plasminogen, cerruloplasmin, choline
esterase; lipoprotein lipase
Enzymes
intracellular – function intracellulary, have no physiological use in
plasma
- membrane bound – ALP, GMT
- cytosolic –
ALT, AST, LD, MDH
- mitochondrial –
AST, GMDH
- lysosomal ACP
- tissue specific – glucose-6-phosphatase – liver
amylase – pancrease
LD1 – heart
•
Healthy individuals - levels of intracellular enzymes fairly constant, low –
the rate of enzyme release from damaged cells into plasma balanced by the
rate of removal of enzyme protein from plasma

Physiological enzyme levels  reference values of the enzyme activities
(determined in clinical laboratory – each lab
has its own reference values)
•
Elevated enzyme activity in the plasma – reflect tissue damage
accompanied by increased release of intracellular enzyme
Skeletal muscle during exertion – physiologically elevated levels of muscle
enzymes in plasma
•
Many diagnostically important enzymes = isoenzymes – pattern of
isoenzymes in plasma (determined electroforetically)
– a means of identifying the damaged tissue
ALTERATION OF ENZYME PLASMA LEVELS
Increased values – increased cell membrane permeability
anoxia, disturbances of energy metabolism 
cytosolic enzymes – ALT, LD, CK
- cell necrosis  membrane-bound enzymes – ALP, GMT
mitochondrial enzymes – AST, GMDH
- induction of the enzyme synthesis  drugs – ALP, GMT
Decreased values – inhibition of the activity  drugs
- inhibition of the synthesis  cell damage, drugs
Examples of enzymes commonly assayed for diagnostic purposes
Enzyme
Location
Cause of elevated plasma level
Acid phosphatase - ACP
Prostate
Prostatic cancer
Alkaline phosphatase – ALP
Bone, liver
Rickets, hypoparathyroidism,
osteomalacia, obstructive
jaundice, cancer of bone/liver
Alanine aminotransferase – ALT
Liver (muscle,
heart, kidney)
Hepatitis, jaundice, circulatory
faillure with liver congestion
Aspartate aminotransferase – AST Heart, muscle,
red cells, liver
Myocardial infarction, muscle
damage, anemia, hepatitis,
circulatory faillure with liver
congestion
Amylase - AM
Pancres
Acute pancreatitis, peptic ulcer
-Glutamyl transferase – GMT
Liver, kidney,
pancreas
Hepatitis, alcoholic liver
damage, cholestasis
Examples of isoenzymes commonly assayed for diagnostic purposes
Enzyme
Creatine kinase – CK
CK-MB
CK-MM
Lactate dehydrogenase – LD
LD1 > LD2
LD2, LD3
LD5
Location
Cause of elevated plasma level
Heart
Skeletal muscle
Myocardial infarction
Muscular dystrophy
Heart, kidney,
blood cells
Myocardial infarction, kidney
disease, megaloblastic anemia,
leukemia
Leukemia
Liver disease, muscle damage
Liver, muscle
ENZYMES IN THERAPY
• Substitution of missing production of digestive enzymes – digestive
enzymes – pepsin trypsin…
• Removal of deposits of death tissue or fibrin (e.g. in lungs, eyes),
treatment of skin defects – proteinases, nucleases, collagenase
•
Acceleration of fibrinolysis in lungs embolization (activation of plasmin
and plasminogen) – streptokinase, urokinase
ENZYMOTHERAPY
Orally administered enzymes – treatment of a variety disorders
- digestive, gastrointestinal, pancreatic
- inflammatory diseases, edema
- immune and autoimmune diseases
(arthritis, multiple sclerosis)
- viral diseases (herpes, AIDS)
- cancer
Mixtures of enzymes of plant and/or animal origin - proteinases, amylase,
lipase - administered as acidoresistent tablets
• Pancreatin – trypsin, chymotrypsin, lipase, amylase
• Wobenzym – pancreatic and plant proteolytic enzymes – trypsin,
chymotrypsin, papain (Carica papaya), bromelain (ananas) =
combination of enzymes with different specificity, pH optimum,
stability, interaction with inhibitors and antiproteinases
 multiple action
• Mechanism of resorption (transport of large macromolecules across the
intestinal barrier) – paracellular transport, receptor mediated endocytosis
and transcytosis
• Mechanism of action – interaction with plasma antiproteinases –
1-antitrypsin, 2-macroglobulin complexes
?
direct proteolytic action, degradation of adhesive
molecules, secretion of cytokins (tranforming growth factor
TGF-), modulation of receptor function
not fully clarified
ENZYMES - USE IN LABORATORY ASSAYS
Enzymes isolated from different sources - used for determination of various
substances in the blood, plasma/serum and urine  enzyme methods
much more specific than chemical methods, the presence of relative
substances with similar chemical properties does not hinder
Components of commercial kits or diagnostic strips
- determination of glucose - glucose oxidase, peroxidase
cholesterol - cholesterol esterase, cholesterol oxidase
peroxidase,
urea – urease, …….
in blood, plasma, serum
- proof of glucose (glucose oxidase), ……..
in blood or urine (strips)
Markes in the immunochemical analysis
- ELISA (=enzyme-linked immunoadsorbent assay) – peroxidase, alkaline
phosphatase
NUCLEOTIDES
Structure, Function
NUCLEOTIDE STRUCTURE
Nucleotides
nitrogenous base + pentose
+
purine
ribose
pyrimidine
deoxyribose
other (nicotinamide)
Nucleosides
phosphate group(s)
1-3
THE NITROGENOUS BASES
Purine bases
NH2
|
C
N
O
||
C
adenine
N
C
HN
CH
HC
C
N
C
CH
C
N
H
N
guanine
H2N
C
N
H
N
Pyrimidine bases
O
||
C
NH2
|
C
O
N
CH
C
CH
N
H
cytosine
O
O
||
C
CH3
HN
C
C
CH
N
H
thymine
HN
CH
C
CH
O
N
H
uracil
NUCLEOSIDE
• A sugar - base combination.
Base
N
O
HOCH2
H
Sugar
In this case
deoxyribose
H
H
OH
H
H
-N-glycosidic
linkage
thymine
O
HN
C
C
H
HN
CH
N
O
OH
H
H
H
H
O
H
C
N
CH
C
CH
H
H
OH
OH
N
O
H
H
OH
OH
CH
N
NH2
|
C
deoxythymidine
C
O
HOCH2
HOCH2
H
C
O
HOCH2
H
O
CH3
C
O
uracil
H
cytidine
cytosine
H
uridine
NH2
|
C
N
adenine
O
N
C
C
HN
CH
HC
C
H2N
C
C
N
O
HOCH2
H
C
H
OH
H
H
H
deoxyadenosine
OH
|
C
N
C
N
H
H
OH
OH
hypoxanthine
CH
HC
C
N
!
O
HOCH2
H
N
H
H
OH
OH
H
inosine
N
O
HOCH2
H
N
CH
N
N
guanine
H
guanosine
NUCLEOTIDES
5’-OH on the sugar of a nucleoside is converted into a
phosphate ester.
NH2
|
C
deoxyadenosine monophosphate
(dAMP)
N
Each is named based on
sugar and base name
and then the number of
phosphates is indicated.
C
N
CH
HC
C
O
||
N
-O-P-O-CH
|
O- -
O
2
H
N
H
H
OH
H
H
ATP - adenosine triphosphate
adenine
phosphate chain
O
-
O
P
O-
O
O
P
O-
NH2
O
O
N
P
O
O-
CH2
N
O
OH
AMP
ADP
ATP
ribose
OH
N
N
NUCLEOTIDE FUNCTION
• Precursors of DNA, RNA - NTPs
• Energy transport
- ATP
• Allosteric effectors of enzymes – ATP, ADP, AMP
• Covalent modification of enzymes – ATP
• Intracellular mediators (= second messengers) – cAMP, cGMP
• Coenzymes – NAD+, NADP+, FAD, CoA-SH
• Activated precursors of polysaccharaides, glycoproteins,
proteoglycans, phospholipids, glycolipids – UDPG, UDPGA,
UDPGal…, CDP-choline, CDP-diacylglycerol…
• Active groups (group transport) – SAM, PAPS
NAD+
reactive
site
O
C
OO
P
O
CH2
O
O
OH
P
O
O
-
ribose
CH2
nicotinamide
N+
NH2
OH
N
O
NH2
N
O
OH
OH
N
N
adenine
FAD
O
H3C
N
H3C
reactive site
NH
N
N
H
C
H
H
C
OH
H
C
OH
H
C
OH
H
C
H
O
riboflavin
NH2
N
O
O
P
O
O
-
ribose
CH2
N
O
OH
OH
N
N
adenine
Coenzyme A
phosphorylated
ADP
pantothenate
unit
NH2
O
O H CH3
C-CH2-CH2-N-C-C-C-CH2
H HO CH3
H-N
O
O
N
P O P O
O-
O- CH 2
O
N
CH2-CH2
S
H
N
Sulfhydryl
group
O
O P OO-
OH
N
CH2 OH
CH2 OH
H
H
OH
O
H
H
OH
H
OH
-D-glucose
H
O
H
OH
O
OH
H
H
H
CH2 OH
OH
-D-glucose
H
O
H
OH
H
H
OH
OH
H
OH
H
O
H C O C
O
H C O C
O
2
O P -O- CH2
-
O
Non-polar tail
cAMP – cyclic adenosine monophosphate
cAMP
NH2
|
C
N
C
N
CH
HC
C
N
O
CH2
-
O
O
P
H
H
O
N
H
H
OH
O-
cAMP – cyclic adenosine monophosphate
-intracellular mediator, second messenger of hormonal signal tranduction
via adenylate cyclase cascade
- mechanism of action: allosteric effector
O
O
O
O
CH2-O-C
C-O-CH
SCoA
SCoA
HO
HO
HO
HO
CH2-O - P ~ P
HO
HO