Enzymes 3
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ENZYMES are ELEVATED IN BLOOD due to
●Increased membrane permeability secondary to injury / damage cells (necrosis) ●intact cells subjected to stress ●released from blocks in their metabolism or excretion ●increased rates of intracellular synthesis and subsequent diffusion of these into the circulation ●enzyme induction
6 Enzyme Classes
Class 1 Oxidoreductases Class 2 Transferases Class 3 Hydrolases Class 4 Lyases Class 5 Isomerases Class 6 Ligases
ENZYME NOMENCLATURE
Numerical designation for each enzyme consisting of 4 numbers separated by periods
ENZYME INHIBITION
No inhibition - Absence of inhibitor Competitive - inhibitor binds to ACTIVE SITE Noncompetitive - inhibitor binds to ALLOSTERIC SITE Uncompetitive - inhibitor binds to E-S COMPLEX
Types of Enzyme Assay
Endpoint Analysis Multipoint Assay Kinetic Assay
Types of Enzyme Assay Endpoint Analysis
= reaction is initiated by the addition of substrate and allowed to proceed for a period of time = measurement of the product or substrate is done at the end of the reaction
Types of Enzyme Assay Multipoint Assay
measures the change in concentration of the substance at several intervals during the course of the assay
Types of Enzyme Assay Kinetic Assay
continuous measurement of change in concentration as a function of time
QC Program for Enzyme Assays
• Strict adherence to zero-order kinetics • Proportionality studies with increments of samples • Use of pooled frozen serum or stable reference materials as controls • Replicate measurements
3 ISO enzymes of creatinine kinase
CK1 most anodal (BB) CK2 (MB) CK3 most cathodal (MM)
Increased after after damaged muscles
myoglobin CK AST LD
COMBINED ISOENZYME ANALYSIS RULE OUT MYOCARDIAL INFARCTION (MI)
CK-MB Absent - 100% predictive value that there refs no MI CK-MB Present & Usual LD - Both Ml and non-MI cases CK-MB Present & Flipped-LD - 100% predictive value that there is MI
Pronounced elevation of CK (5 or more times Normal)
● Duchenne’s muscular dystrophy ●polymyositis ●dermatomyositis ●AMI
Mild or moderate elevation (2-4 times Normal) of CK
●severe exercise, trauma, surgical procedure, IM injections ●delirium tremens, alcoholic myopathy ●MI, severe iochemic injury ●pulmonary infarction ●pulmonary edema ●hypothyroidism ●acute agitated psychoses
Isoenzyme & tissue rich in lactate dehydrogenase
LD1 heart, brain, RBC LD2 heart, brain, RBC LD3 brain, kidney, lung LD4 liver, skeletal muscle, kidney LD5 liver, skeletal muscle, kidney
CONDITIONS AFFECTING TOTAL LD ACTIVITY Pronounced Elevation (5 or more times Normal)
● Megaloblastic anemia ●Widespread carcinomatosis, esp. hepatic metastases ●Septic shock and hypoxia ●Hepatitis ●Renal infarction ●Thrombotic thrombocytompenic purpura
CONDITIONS AFFECTING TOTAL LD ACTIVITY Moderate Elevation (3-5 times Normal)
● MI ●Pulmonary infarction ●Hemolytic conditions ●Leukemia ●IM ●Delirium tremens ●Muscular dystrophy