Transcript CLINICAL CHEMIISTRY (MT 305) CARBOHYDRATE LECTURE ONE

Major Enzymes of
Diagnostic Interest
Dr. Essam H. Jiffri
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Phosphatases
Acid Phosphatase
- The richest source of acid phosphatase is the
prostate, significant amounts are also found in
erythrocytes, liver, spleen and platelets.
- Diagnostically, acid phosphatase measurements
are used for monitoring metastatic carcinoma of
the prostate serum levels .
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Acid Phosphatase
- Some acid phosphatase is released into the
circulation when the prostate is examined per
rectum (P.R) and blood should be taken before
this examination.
- Serum acid phosphatase may be increased
through nonprostatic causes, these include
haemolysis, bone disease, particularly Paget's
disease and metastatic carcinoma of the breast.
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Acid Phosphatase
Prostate-Specific Antigen
- Prostate-specific antigen (PSA) found in prostatic
tissue and is raised in serum in a higher
proportion in cases of metastatic carcinoma than
acid phosphatase
- It is a more sensitive but less specific indicator of
metastatic prostatic carcinoma.
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Alkaline Phosphatase
- Alkaline phosphatase is found in liver, bone,
intestine, placenta and kidney, the main sources
of serum enzyme are the hepatobiliary tree and
osteoblasts.
- Physiologically increased levels are seen during
periods of active bone growth, particularly in
infants and at puberty.
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Alkaline Phosphatase
- Values increase during the second and third
trimesters of pregnancy to about twice those
normally seen in adults.
- Pathologically increases in serum alkaline
phosphatase occur mainly in hepatobiliary
disease and bone disease.
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Alkaline Phosphatase
-To identify the tissue of origin by determining
alkaline phosphatase isoenzymes or by estimating
the activity of another enzyme, usually Gammaglutamyl transferase, which rises in parallel with
biliary alkaline phosphatase.
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Alkaline Phosphatase
- Alkaline phosphatase activity in serum is usually
estimated to detect increased levels, but
markedly reduced levels are found in the
inherited condition (hypophosphatasia), which is
caused by defective bone calcification.
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Transaminases
Aspartate Aminotransferase
- Aspartate aminotranferase (AST) is widely
distributed, the heart, liver, skeletal muscle and
kidney being rich sources.
- Smaller amounts are found in erythrocytes and
slight increases can occur in haemolysis.
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Transaminases
Aspartate Aminotransferase
- The major diagnostic applications are in the
investigation of myocardial infarction, liver
disease and muscle disease.
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Transaminases
Alanine Aminotransferase
- Alanine aminotransferase (ALT) is also widely
distributed, the largest amounts occur in liver.
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Transaminases
Alanine Aminotransferase
- Smaller amounts occur in the heart and ALT
usually remains normal following myocardial
infarction unless congestive cardiac failure
occurs, causing release from the liver.
- ALT is more specific for liver disease than AST.
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Abnormalities of AST and ALT in
various disease states
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Skeletal
Muscle
Injury
AMI
CHF
Hepatitis
AST
↑ or ↑↑
↑ or ↑↑
↑ or ↑↑
↑↑↑
↑
↑
ALT
→
→
↑ or ↑↑
↑↑↑
↑
↑
Cirrhosis Biliary
Obstruction
Gamma-glutamyl Transferase
- Gamma-glutamyl transferase (GGT) is found in
several tissues, the kidney being the richest
source.
- Significant amounts are present in the liver and
pancreas, the major diagnostic application of
GGT measurements in the investigation of
hepatobiliary disease.
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Gamma-glutamyl Transferase
- Elevations in serum levels (70-80%) of patients
who abuse alcohol, with more marked elevations
occurring in the presence of alcoholic liver
disease.
- Gamm-glutamyl transferase is a less sensitive
indicator of hepatocellular disease than
transaminases but high serum levels occur in
cholestasis.
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Gamma-glutamyl Transferase
- Serum GGT activity sometimes increases
following myocardial infarction and in congestive
cardiac failure, this is probably due to hepatic
congestion.
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Amylase
- Amylase is a digestive enzyme, hydrolyzes
glycosidic bonds in polymers of glucose, such as
starch and glycogen, to produce maltose and
other polysaccharides and dextrins.
- Amylase is produced by the pancreas and
salivary glands and its main diagnostic
application is in the investigation of acute
abdominal pain.
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Amylase
- The main source of elevated serum amylase
activity is the pancreas.
- Conditions causing increased levels of amylase:
o
o
o
o
o
o
o
o
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Pancreatitis
Renal insufficiency
Ovarian malignancy
Ectopic pregnancy
Salpingitis
Lung carcinoma
Cardiac surgery
Mumps
Amylase
- Serum amylase activities greater than 10 times
the upper limit of normal are diagnostic of acute
pancreatitis.
- Elevated amylase activity may also be due to
macroamylasemia (amylase is bound to immunoglobulin typically IgG in serum).
- Patients with macroamylasemia evaluated using
amylase:creatinine clearance ratio (ACCR).
- The ACCR is typically increased in acute
pancreatitis.
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Lipase
- Lipase is also a digestive enzyme secreted by
the pancreas.
- Catalyzes the hydrolysis of ester bonds in
triglycerides to produce fatty acids and 2acylglycerol.
- Lipase along with amylase is utilized in the
diagnosis of pancreatitis.
- In the past, amylase was the test of choice for
the diagnosis of pancreatic disease.
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Lipase
- Lipase is now considered to be more sensitive
and specific than amylase as a marker of
pancreatitis.
- In patient with acute pancreatitis, lipase increased
sooner and usually remains elevated for a longer
period of time compared to amylase.
- Pancreatic lipase has at least three isoforms.
- Lipase isoforms provide more accurate diagnostic
information than the measurement of total
enzyme activity.
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Lipase
- Lipase in the peripheral circulation is
removed via glomerular filtration and is
completely reabsorbed by proximal tubule
and not normally excreted in urine.
- In patient with acute pancreatitis, lipase
value > 10 times the upper limit of the
reference interval and characterized as
being pathogenic for the disease.
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Cholinesterase
Two types of cholinesterase are found in man:
• Acetylcholinesterase (AChE) also referred to as:
true or RBC cholinesterase
• Serum cholinesterase (SChE) also referred to as:
– Pseudocholinesterase or
– Acylcholin acylhydrolase
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Tissues Containing the Cholinesterases
AChE:
o
o
o
o
Nervous system
Erythrocytes
Lungs
Spleen
SChE:
o
o
o
o
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Serum
Heart
Liver
Pancrease
Cholinesterase
Cholinesterase Deficiency
- Cholinesterase is synthesized in the liver and
serum levels are often low in hepatic disease.
- Organophosphorus insecticides, which are used in
sheep dips, inhibit both cholinesterases and
serum cholinesterase can be used to screen for
poisoning.
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Creatine Kinase
- CK catalyses the phosphorylation of creatine.
- The richest source of the enzyme is skeletal
muscle while cardiac muscle and brain.
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Tissues Containing Highest Levels of CK
o
o
o
o
o
o
o
o
o
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Skeletal muscle
Cardiac muscle
Brain
Smooth muscle of the colon
Small intestine
Uterus
Prostate
Lungs
Kidneys
Conditions Causing a Marked Elevation
in Total CK Activity
o
o
o
o
o
o
o
o
o
o
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Acute myocardial infarction
Muscular dystrophy
Intramuscular injection
Pregnancy
Strenuous exercise
Surgery
Trauma
Myopathies
Hypothyroidism
Neoplastic disorders of the prostate,gastrointestinal
tract,or bladder
Creatine Kinase
- The main diagnostic application of CK is in the
investigation of muscle disease, when the major
circulating isoenzyme is CK-MM, and myocardial
infarction, in which CK-MB predominates.
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Lactate Dehydrogenate
- Most tissues contain LDH and therefore
measurements of the enzyme have low
specificity.
- LD composed of combination of two subunits
designated H (heart) amd M (muscle), this may
be improved by determining isoenzymes; five
forms occur, the proportions of which vary
between tissues.
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Tissue Specificities of the LD
Isoenzymes
• Predominant isoenzymes in myocardium and
erythrocytes
- LD-1 (HHHH)
- LD-2 (HHHM)
• Predominant isoenzymes in lungs and spleen
- LD-3 (HHMM)
- LD-4 (HMMM)
• Predominant isoenzymes in liver and skeletal
muscle
- LD-5 (MMMM)
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Lactate Dehydrogenate
- Isoenzymes can be determined by
electrophoresis which separates different forms
on the basis of their electrical charge, heart
having a high proportion of fast-moving enzyme,
while the least mobile form predominates in
liver.
- The main diagnostic application of LDH
measurements is in the investigation of
myocardial infarction.
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Lactate Dehydrogenate
- LDH catalyses the reversible oxidation of Llactate to pyruvate but also has activity against
other hydroxy- and keto-acids, including
hydroxybutyrate (2-oxobutyrate).
- The cardiac isoenzyme has a high affinity for this
substrate, while liver LDH reacts with it very
slowly; therefore, the cardiac isoenzyme may be
determined by measuring hydroxybutyrate
dehydrogenase (HBD) activity.
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Enzyme
Origin
Main applications
Acid phosphatase
Prostate, erythrocytes
Metastatic carcinoma of
prostate
Alanine aminotransferase (ALT,
SGPT)
Hepatocytes
Kidney
Hepatocelluar disease
Alkaline phosphatase (ALP)
Hepatobiliary tree
Bone
GI tract, placenta, kidney
Cholestatic disease
Bone disease
Lipase
Amylase
Pancrease
Pancrease, Salivary glands
Acute pancreatitis
Acute pancreatitis
Aspartate aminotransferase (AST,
SGOT)
Hepatocytes
Cardiac muscle
Skeletal muscle
Hepatocelluar disease
Myocardial infarction
Muscle disease
Cholinesterase
Liver
Organophosphorous
poisoning
Creatine kinase (CK)
Skeletal Muscle
Heart Muscle
Brain
Muscle disease
Myocardial infarction
y-Glutamyl transferase (GGT)
Liver
Pancrease
Kideny
Cholestasis
Alcohol abuse
Lactate dehydrogenase (LDH)
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Cardiac muscle
Skeletal muscle
Erythrocytes, liver
Myocardial infarction