5 3.Isozymes or Isoenzymes: Different form of the same enzyme.They perform the same catalytic function.(Catalyze same reactions but are formed from structurally different polypeptides).Different Isoenzymes may arise from different tissues and their specific detection may give clues to the site of pathology.
6 Functional plasma enzymes ( Plasma derived enzymes)Certain enzymes, proenzymes, and their substrates are present at all times in the circulation of normal individuals and perform a physiologic function in the blood.Examples of these functional plasma enzymes include the proenzymes of blood coagulation.The majority of these enzymes are synthesized in and secreted by the liver.Nonfunctional plasma enzymes(Cell derived enzymes)-Plasma also contains numerous other enzymes that perform no known physiologic function in blood.Arise from the routine normal destruction of erythrocytes, leukocytes, and other cells.
7 Tissue damage or necrosis resulting from injury or disease is generally accompanied by increases in the levels of several nonfunctional plasma enzymes.
9 How? of numerous enzymes has been shown The measurement of the serum levelsof numerous enzymes has been shownto be of diagnostic significance.This is because the presence of these enzymes in the serum indicates thattissue or cellular damage has occurred resulting in the release of intracellular components into the blood &this increases the level of certain enzymes in blood according to the damaged organ.
10 Information from enzymes measurements in serum? Presence of disease.Organs involved.Etiology /nature of disease: differential diagnosis.Extent of disease-more damaged cells-more leaked enzymes in blood.
11 Measurement of enzyme activity Enzyme activity is expressed in International unit (IU):-It corresponds to the amount of enzymes that catalyzes the conversion of one micromole (mol) of substrate to product per minute.
12 What are the enzymes most used the diagnosis of certain diseases?
14 Lactate dehydrogenase(LDH) Lactic acidPyruvic acidNADNADH+HLDH is elevated in myocardial infarction, blood disorders.It is a tetramer protein and made of two types of subunits namely H = Heart, M = skeletal muscle.It exists as 5 different isoenzymes with various combinations of H and M subunits.
17 Creatine kinase (CK) Creatine Creatine phosphate ATPADP(Phosphocreatine – serves as energy reserve during muscle contraction)Creatine kinase is a dimer made of 2 monomers.Skeletal muscle contains M subunit, Brain contains B subunits.Three different isoenzymes are formed.
18 CK-1 BB CK-2 MB CK-3 MM Isoenzyme name Composition Present in Elevated inCK-1BBBrainCNS diseasesbrain tumorsCK-2MBHeartAcute myocardial infarctionCK-3MMSkeletal muscleSkeletal muscle diseases
20 Alanine transaminase(ALT) It is also calledSerum glutamic pyruvic transaminase(SGPT).This enzyme is found predominantly in hepatocytes.It increases in liver & heart diseases.ALT is more specific for liver disease than AST.
21 Glutamic oxalacetic transminase(SGOT) Aspartate transaminase(AST)Glutamic oxalacetic transminase(SGOT)*It is also calledSerum glutamic oxaloacetic transaminase(SGOT)*It increases in liver & heart diseases.
23 **It is found in the bone , liver, intestine, placenta. Alkaline phosphatase**It is found in the bone , liver, intestine, placenta.**Increases mainly in bone and liver diseases.Acid phosphatase**is found in the prostate, red blood cells, bone, liver, and pancreas.** Mostly used to detect prostatic carcinoma.**Amylase and lipase enzymes increase in diseases of the pancreas as acute pancreatitis
24 Summary-Enzymes as diagnostic markers Major diagnostic useOriginEnzymeMyocardial infarctionHeart, liver, muscle, RBCLactate dehydrogenase (LDH)Muscle diseaseSkeletal MuscleHeart MuscleBrainCreatine kinase (CK)Viral hepatitisHeart and LiverAlanine aminotransferase (ALT) Serum glutamate-pyruvate transaminase (SGPT)Liver and heart diseaseAspartate aminotransferase (AST)Serum glutamate-oxaloacetate transaminase (SGOT)Liver and bone diseaseHepatobiliary treeBone, placentaAlkaline phosphatase (ALP)Prostate cancerProstate, erythrocytesAcid phosphatase (ACP)Acute pancreatitisPancreas, Salivary glandsAmylasePancreasLipase