Enzymes 3 Flashcards
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
