بسم الله الرحمن الرحيم. Dr.Rania F. Eltelbany. 1.
Dr.Rania F. Eltelbany. 2. Dr.Rania F. Eltelbany Lecturer of Biochemistry Faculty of Pharmacy MTI University.
Measurement of some selected enzymes in plasma for the detection, diagnosis and monitoring of diseases..
Enzymes are catalysts that increase the rate or velocity of physiologic reactions. Most enzymes are present in cells at much higher concentrations than in plasma ..
Classification of enzymes:. Plasma specific enzymes Secreted enzymes Cellular enzymes Lipase, α- amylase (Pancreatic digestive enzymes), Trypsinogen, prostatic acid phosphatase (PAP). Procoagulants and fibrinolytic enzymes: (clotting factor), plasminogen and the lipid substrate enzyme LPL and LCAT. Lactate dehydrogenase (LDH), Aminotransferases (AST, ALT), Alkaline phosphatases (ALP). Normally intracellular and leak out upon damage..
Enzymes present in Plasma :. Functional Plasma enzymes Non-functional plasma enzymes Mostly synthesized by the liver cholinesterase Plasminogen.
Selection of the enzyme tests: The selection of which enzyme to measure in serum for diagnostic or prognostic purposes depends on a number of factors. An important one is the distribution of enzymes among the various tissues. The main enzymes of established clinical value are listed in the following table:.
Distribution of enzymes among tissues Rate of disappearance of enzymes from blood. Ease of assay. Cost of assay. Quantity in blood..
Isoenzymes are different forms of the same enzyme. They share the same type of reaction. They differ in structure, activity, km, physical properties, expression in various cells and tissues in the body..
Different isoenzymes in plasma may arise from different tissues and their detection may give clues to the site of pathology. Examples: Alkaline phosphatase isoenzymes may distinguish between bone and liver disease. A specific isoenzyme of creatine kinase (CK-MB) is useful in early detection of myocardial infarction..
I) Serum enzymes of acute myocardial infarction (MI) : Creatine kinase (CK) , L actate dehydrogenase (LDH) , a spartate aminotransferase (AST), ß-h ydroxybutyrate dehydrogenase ( ß-HBDH). II) Serum enzymes in liver diseases and jaundice : A minotransaminases (ALT,AST), Alkaline phosphatase (ALP), y-glutamyl transferases (GGT), B ilirubin . III) Enzymes in serum and urine for pancreatic diseases: Acute pancreatitis and Chronic pancreatitis ..
IV) Enzymes used in patients with cancer: Acid phosphatase (ACP), Alkaline phosphatase (ALP), Creatine kinase-BB (CK-BB), Gamma-glutamyl transferase (GGT), Lactate dehydrogenase (LDH), Lysozyme ( muramidase ), 5 ’-Nucleotidase, Pancreatic enzymes (amylase, lipase, ribonuclease, trypsin), Phosphohexose isomerase (PHI), Terminal deoxynucleotidyl transferase (TDT) . V) Enzyme tests in bone disease : Alkaline phosphatase (ALP) , Tartarate resistant acid phosphatase ( TrACP ) ..
What is MI?. It is when blood flow decreases or stops to a part of the heart, causing damage to the heart muscle ( loss of blood supply). It is almost always caused by the atherosclerosis of the coronary arteries..
Symptoms of MI:. Dr.Rania F. Eltelbany. 14. 1- Chest Pain 2-Marked Sweating 3-Nausea & vomiting 4-Abnormal BP & Heart Rhythm.
About 25% of all MI may be “ silent ”, associated either within atypical symptoms or no symptoms at all diabetic neuropathy. Chest pain , may be due to causes other than myocardial infarction. Chest pain may also have an emotional origin such as in depression and anxiety ..
Dr.Rania F. Eltelbany. 16. Heart Attack illustration Myocardial Infarction.
When myocardial cells die, they break up and release their contents. The cardiac markers commonly used to diagnose MI are:.
It is an enzyme that reversibly catalyses the reaction : ATP + c reatine ADP + Creatine phosphate In human tissues, CK is a dimeric enzyme composed of b (brain) & m (muscle) units and 3 isoenzymes are present : CK-BB , CK-MB, CK-MM CK-MM are found in heart muscle , the diaphragm and especially in skeletal muscle. This forms 97% of total CK activity. CK-MB is predominantly found in cardiac muscle and also in skeletal muscle and diaphragm. These forms 0-3% of the total activity . CK-BB is the only isoenzyme found in brain tissue and is also present in the prostate, bladder and intestine ..
Muscle Trauma : CK-MB/ Total CK = < 3% MI : CK-MB/ Total CK = > 6% Proper diagnosis of AMI require samples to be collected at appropriate time intervals. Samples should be drawn on admission and at 6 hrs , 12 hrs and 24 hrs when AMI is suspected. Serum CK begins to rise after 3-6 hr of MI and reaches a maximum at 24 hrs ( the higher the rise, the worse is the prognosis). It returns normal 3-4 days . further increase indicates extension of infarct..
It is involved in glucose metabolism and occurs in all organ cells in man but is especially many in cardiac and skeletal muscle, liver, kidney and red blood cells . LDH Isoenzymes: LDH Is tetrameric enzyme, composed of 4 subunits of two types – H (“heart”) and M (“muscle”). Thus five LDH Isoenzymes exist..
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Corresponding to LDH-I to LDH-5 respectively : Cardiac muscle is richest in LDH-I and LDH-2 MI In liver LDH5 is the most plentiful . Normally, LDH2 >LDH1 , but with MI , this pattern is " flipped " and LDH1 >LDH2 occur at 12-24 hrs after MI and may persist for several days. LDH-1 & LDH-2 may be seen when the total LDH activity is within normal limits..
It is an important enzyme in amino acid metabolism. AST values can persist for about 4 days after infraction. AST < specific than LDH elevation, but it can provide helpful information when hospital admission is delayed, or the time of onset is unknown. The begins 3-8 hrs after the onset of the attack. The highest values are found on average 24 hrs after the onset. The duration and extent of the increase related to the size of the infarct. Values are most commonly from 1-5 times the upper reference limit..
In serum, commonly found ketone bodies include acetoacetic acid, acetone and ß-hydroxybutyric acid. Acetoacetate and ß-hydroxybutyrate are interconverted by the mitochondrial enzyme ß-hydroxybutyrate dehydrogenase , which is present in many tissues including the heart. This enzyme plays an important role in the synthesis and degradation of ketone bodies (ketosis) and in keeping the redox state of the mitochondrial NAD system within normal..
1) Serum enzymes as diagnostic indicator of acute MI:.
B) Cardiac proteins of cardiac muscle :. 1) Serum Myoglobin (MB): 2) Serum Troponin Complex :.
Oxygen binding protein present in cytoplasm of all muscle cells . Its small size and cytoplasmic location (17.6 KD a molecular wt.) “ earliest marker of cardiac damage ”. It is not a specific marker because : The structural similarity between MB present in cardiac & skeletal muscle. Its kidney clearance (12-24 hr)..
Image result for troponin. Troponins are proteins that regulate muscle contraction . Troponin complex has three subunits: Troponins C, I & T. Two isoforms of T & I are specific to myocardium ..
It is possible with troponins to detect infarctions that are much smaller than those detectable with other cardiac markers..
Investigation of Suspected MI According to Onset Time of Symptoms within 3 h ECG Diagnosed MI ECG Equivocal MI 12-24 h ECG Equivocal MI 6-12 h 24 h -Later ECG Equivocal MI ECG Diagnosed MI 6 h ECG Equivocal MI ECG Diagnosed MI ECG Diagnosed MI ECG Diagnosed or Equivocal 1- Mb 2- CK-MB 1- Mb & CK-MB 2- Troponin (T-I) 1- CK-MB 2- Troponin (T-I) 1- CK-MB 2- Troponin (T-I) Troponin (T-I ).
Image result for comparison of sequential changes in serum CK,Myoglobin, AST, LDH after myocardial infarction.
Dr.Rania F. Eltelbany Lecturer of Biochemistry Faculty of Pharmacy MTI University.