Clinical Biochemistry

1. Dr. Mohammad Shiblee Zaman
Lecturer (Biochemistry)
Dhaka Medical College
Clinical enzymology

2. Clinical enzymology
Deals with study of enzyme activity for diagnosis
and prognosis of diseases

3. Plasma enzymes
Depending on their source and function –
Functional plasma enzymes
Nonfunctional plasma enzymes

4. Functional plasma enzymes
 Concentration is very high in plasma
 Synthesized by the liver
 High catalytic activity in plasma
 Plasma-derived enzymes
 eg. fibrinogen, prothrombin, lipoprotein lipase,
cholinesterase, ceruloplasmin, plasminogen,
plasminogen activator etc.

5. Nonfunctional plasma enzymes
 Concentration very low in plasma
 Synthesized by RER in cells
 No specific function in plasma
 Cell-derived enzymes
 Either secretory (functions outside blood, in
lumen of GIT) eg. lipase, amylase, tripsinogen
etc. or intracellular eg. SGPT, SGOT, CK etc.

6. Sources in plasma
Nonfunctional enzymes
continuously discharging into
plasma by –
1. Normal diffusion through
cell membrane
2. Normal cell death (cellular
turnover)

7. Patho-physiology of excess
 Balance exists between rate of post-synthetic
influx of an enzyme in plasma and its catabolism
and clearance from plasma.
 Disease causes imbalance by either increasing
release or decreasing clearance from plasma.

8. Factors affecting enzyme concentrations
in plasma or serum
 Leakage of enzymes from cells
 Efflux of enzymes from damaged cells
 Altered enzyme production
 Clearance of enzymes

9. Significance of clinical enzymology
 Diagnosis of disease
 Pattern of disease
 Prediction of severity of disease
 Prognosis of disease
 Differential diagnosis

10. Distribution of diagnostically important enzymes
Enzyme Sources Clinical Applications
ALT Liver Liver disease
ALP Liver, bone, intestinal mucosa,
placenta
Hepatobiliary disease,
bone disease
GGT Liver, pancreas, kidney Hepatobiliary disease
5′-NT Liver Hepatobiliary disease

11. Distribution(contd.)
Enzyme Sources Clinical Applications
AST Heart, liver, RBC,
skeletal muscle
Cardiac disease, liver disease,
muscle disease, hemolytic anemia
CK Skeletal muscle,
heart, brain
Muscle disease, cardiac disease
LDH Heart, RBC, liver,
lymph nodes,
skeletal muscle
Hemolytic and megaloblastic anemias,
leukemia & lymphomas, oncology

12. Distribution(contd.)
Enzyme Sources Clinical Applications
Amylase Salivary glands,
pancreas
Pancreatic disease,
sialedenitis
Lipase Pancreas Pancreatic disease
Acid phosphatase Prostate, RBC, bone Ca prostate,
bone disease
Aldolase Skeletal muscle,
neoplastic tissue
Muscle disease,
leukemia

13. Nature : Dimeric enzyme
Types with
distribution
: CK-1 (CK-BB)
CK-2 (CK-MB)
CK-3 (CK-MM)
cytosol of cells
CK-Mt IMM
Creatine Kinase

14. Concentrations of tissue CK
Tissue CK-BB or
CK-1
CK-MB or
CK-2
CK-MM or
CK-3
Skeletal muscle <1% 1-3% 97-99%
Heart <1% 22% 78%
Brain 100% 0% 0%
Smooth Muscle
(GIT, UB)
92-96% 1-6% 2-3%

15. Clinical Significance
Increase serum concentration during injury,
inflammation or necrosis of skeletal or heart
muscle

16. Kinetics in acute pancreatitis
Enzyme Initial rise Peak Returns to normal
Amylase 6 – 12hr 12 – 72hr 24 – 48hr (after that urinary
amylase: creatinine ratio)
Lipase 4 – 8hr 24hr 7 – 14d

17. Cardiac markers

18. Cardiac markers
Intracellular proteins
Released into blood following cardiac muscle
damage
Most commonly due to myocardial infarction

19. Characteristics of ideal cardiac marker
Cardio-specific
Highly sensitive
Normally absent or present in trace amount in blood
Rise of serum level proportional to extent of damage
Persist in blood for a reasonable period
Easy to measure
Cost effective

20. Cardiac markers
Enzymes
CK-MB
AST
LDH
Proteins
Troponin I
Troponin T
Newer markers
BNP
hs-CRP
MPO

21. Troponin
Contractile protein complex
Located in striated muscle (94-
97% in myofibrils, 3-6% in cyto
plasm)
Three subunits

22. Subunits
Troponin
Tn I
Actinomyosin
ATPase inhibitory
element
Tn T
Tropomyosin
binding element
Tn C
Ca2+ binding
element

23. Cardiac specificity
 All three subunits has multiple isoforms
 Cardiac and skeletal isoforms of TnC are identical
 cTnI has additional 31 N-terminal AA residue compared to
skeletal isoform (completely cardio-specific)
 cTnT has additional 11 N-terminal AA residue compared to
skeletal isoform; may also increase in muscular dystrophy,
polymyositis, dermatomyositis etc. (cardio-specific)

24. Kinetics in acute myocardial infarction
Marker Initial rise Peak Returns to normal
Myoglobin 2 – 4hr 12 – 24hr 2 – 4d
cTnI 4 – 6hr 12 – 24hr 14d
CK-MB 4 – 6hr 12hr 2 – 3d
AST 6 – 8hr 24 – 486hr 2 – 4d
LDH 12 – 24hr 48 – 72hr 7 – 12d

25. Kinetics of cardiac markers