Clinical Enzymes: Functions and Applications

# ... ## 1. Acid Phosphatase ### **Basic Function** - **Primary Role**: Hydrolysis of phosphate esters at acidic pH (5-6) - **Location**: Lysosomes (cytoplasmic enzyme) - **Distribution**: Prostate gland, liver, spleen, RBC, platelets ### **Clinical Applications** - **Prostate Cancer Screening**: Primary diagnostic tool for prostate carcinoma in males <35 years - **Forensic Medicine**: Confirmatory test for sexual assault cases - **Cancer Detection**: Identifies ectopic sources in breast cancer and other malignancies ### **Sample Collection & Analysis** - **Sample Type**: Plasma with citrate anticoagulant (pH 6.2-6.6) - **Critical Points**:Avoid hemolysis (RBC contain high levels) - Rapid platelet separation required - pH and heat labile enzyme ### **Clinical Significance** - **Age Variations**: Newborns have 2-3x higher levels than adults - **Gender Differences**: Adult males show ¼ to ½ of total plasma levels from prostate - **Interference**: Fluoride inhibits activity; oxalates and heparin reduce levels --- ## 2. Creatine Kinase (CK) ### **Basic Function** - **Primary Role**: Energy metabolism through ATP breakdown - **Reaction**: Creatine + ATP ⇌ Phosphocreatine + ADP - **Distribution**: Cardiac muscle, skeletal muscle, brain ### **Isoenzyme Profile** **CK-MM (M₂)** → Skeletal & cardiac muscle ⟨Half-life: 15 hours⟩**CK-MB (MB)** → Cardiac muscle exclusively ⟨Half-life: 12 hours⟩**CK-BB (B₂)** → Brain tissue ⟨Half-life: 3 hours⟩ ### **Clinical Applications** - **Myocardial Infarction**: CK-MB peaks 2 days post-attack, returns to normal by day 4 - **Muscle Disorders**:Muscular dystrophy - Polymyositis - Skeletal muscle damage - **Neurological Conditions**:Cerebral thrombosis - Brain infarction - Cerebral embolism ### **Sample Requirements** - **Sample Type**: Serum only (anticoagulants inhibit activity) - **Storage**: Protect from light (light-labile enzyme) - **Normal Variations**: Males > females (higher muscle mass) --- ## 3. γ-Glutamyl Transferase (GGT) ### **Basic Function** - **Primary Role**: Amino acid transport and glutathione metabolism - **Distribution**: Biliary ducts (liver), kidney, pancreas ### **Clinical Applications** - **Liver Disease Diagnosis**:Proportional marker for liver damage - Elevated in obstructive jaundice and hepatitis - Combined with alkaline phosphatase and ALT for confirmation - **Alcohol Monitoring**:**Most Important Application** - Production proportional to alcohol consumption duration - Sensitive indicator of chronic alcohol use - **Kidney Function**: Elevated urinary GGT indicates renal damage ### **Sample Collection** - **Sample Type**: Serum (citrate, oxalate, fluoride inhibit activity) - **Interference**: Heparin causes turbidity affecting spectrophotometric analysis ### **Factors Affecting Levels** - **Gender**: Males > females - **Age**: Newborns > adults - **Drugs**: Anticonvulsants, barbiturates, aminoglycosides increase levels - **Conditions**: Gross obesity elevates GGT --- ## 4. Lactate Dehydrogenase (LDH) ### **Basic Function** - **Primary Role**: Lactate ⇌ Pyruvate conversion - **Reaction**: Lactate + NAD⁺ ⇌ Pyruvate + NADH + H⁺ - **Distribution**: Kidney, heart, skeletal muscle, brain, liver, lungs ### **Isoenzyme Profile** **LDH₁ (H₄)** → Cardiac muscle ⟨17.5-28.3%⟩ • *Myocardial infarction marker***LDH₂ (H₃M)** → Cardiac muscle ⟨30.4-36.4%⟩ • *Cardiac damage indicator***LDH₃ (H₂M₂)** → Lungs ⟨19.4-24.2%⟩ • *Pulmonary infarction marker***LDH₄ (HM₃)** → Kidney ⟨9.6-15.6%⟩ • *Renal damage indicator***LDH₅ (M₄)** → Skeletal muscle, liver ⟨5.5-12.7%⟩ • *Liver damage marker* ### **Clinical Applications** - **Myocardial Infarction**:**"Flipped Pattern"**: LDH₁ > LDH₂ (normally LDH₂ > LDH₁) - Develops 24 hours post-infarction - Persists 1-2 days then reverts to normal - **Organ-Specific Damage**:Lung damage: Elevated LDH₃ - Liver damage: Elevated LDH₅ - General tissue damage indicator ### **Sample Requirements** - **Sample Type**: Serum (oxalates inhibit activity) - **Storage**: Avoid freezing (destroys isoenzymes) - **Interference**: Avoid hemolysis (RBC contain significant LDH) --- ## 5. Aminotransferases (AST & ALT) ### **Basic Function** - **Primary Role**: Amino group transfer between amino acids and keto acids - **Reversible catalysis**: Essential for protein metabolism ### **Distribution & Specificity** **AST (SGOT)** → Heart, liver ⟨: 6-18 U/L | : 7-21 U/L⟩ • *Cardiac & hepatic damage***ALT (SGPT)** → Liver (primary) ⟨: 4-17 U/L | : 6-24 U/L⟩ • *Liver-specific marker* ### **Clinical Applications** - **Liver Disease**:Viral hepatitis: Remarkable increase in both enzymes - ALT > AST in liver inflammation (greater liver specificity) - ALT used for blood bank screening (hepatitis detection) - **Cardiac Conditions**: AST elevation in myocardial damage - **Other Applications**: AST in pulmonary embolism ### **Sample Collection** - **Sample Type**: Serum or plasma (no anticoagulant inhibition) - *