Enzymes

This section outlines the role of enzymes in diagnostics. Accurate measurement of enzyme activity and its interpretation can provide critical insights into a range of diseases

Biochemical Theory and Physiology

• Enzymes as Biological Catalysts: Accelerate biochemical reactions
• Structure and Function: Active site, cofactors, coenzymes
• Enzyme Kinetics: Michaelis-Menten Kinetics, Vmax, Km
• Factors Affecting Enzyme Activity: pH, temperature, inhibitors, activators
• Regulation of Enzyme Activity: Allosteric regulation, covalent modification
• Enzymes in Metabolic Pathways: Key roles in glycolysis, Krebs cycle, etc
• Isoenzymes: Different forms of the same enzyme with tissue-specific distribution

Laboratory Test Procedures

• Types of Enzyme Assays
  • Kinetic Assays (Continuous Monitoring): Measure the rate of reaction
  • Fixed-Time Assays (Endpoint Assays): Measure product formed after a set time
• Commonly Measured Enzymes
  • Cardiac Markers: Creatine Kinase-MB (CK-MB), Troponin
  • Liver Enzymes: Alanine Aminotransferase (ALT), Aspartate Aminotransferase (AST), Alkaline Phosphatase (ALP), Gamma-Glutamyl Transferase (GGT)
  • Pancreatic Enzymes: Amylase, Lipase
  • Muscle Enzymes: Creatine Kinase (CK)
  • Others: Acid Phosphatase, Angiotensin-Converting Enzyme (ACE)
• Special Precautions
  • Proper Specimen Collection
  • Timely Specimen Processing and Handling
  • Strict Adherence to QC Procedures
• Analytical Techniques
  • Spectrophotometry
  • Immunoassay
  • Enzyme-Linked Immunosorbent Assay (ELISA)

Test Result Interpretation

• Establish Reference Intervals
• Elevated Levels: Indicate tissue damage or increased production
• Isoenzyme Patterns: Aid in identifying the source of the elevated enzymes
• Clinical Correlation: Integrate lab results with clinical presentation and patient history
• Factors Affecting Interpretation: Medications, hemolysis, lipemia

Disease State Correlation

• Cardiac Disorders
  • Myocardial Infarction: Elevated CK-MB and Troponin
• Liver Disorders
  • Hepatitis: Elevated ALT and AST
  • Alcoholic Liver Disease: Elevated AST and GGT
  • Biliary Obstruction: Elevated ALP and GGT
• Pancreatic Disorders
  • Pancreatitis: Elevated Amylase and Lipase
• Muscle Disorders
  • Rhabdomyolysis: Elevated CK
• Other Disorders
  • Prostate Cancer: Elevated Acid Phosphatase
  • Sarcoidosis: Elevated Angiotensin-Converting Enzyme (ACE)

Putting it All Together

• Enzyme assays can be affected by a number of things, so accurate collection and running is important
• Review what factors can influence these tests to get the most accurate and complete clinical picture for the patient
• Connecting enzyme biochemistry with disease states is essential for accurate diagnosis and treatment