Presentation on theme: "1 Major Enzymes of Diagnostic Interest Dr. Essam H. Jiffri."— Presentation transcript:
1 Major Enzymes of Diagnostic Interest Dr. Essam H. Jiffri
2 Phosphatases Acid Phosphatase - The richest source of acid phosphatase is the prostate, significant amounts are also found in erythrocytes, liver, spleen and platelets. - Diagnostically, acid phosphatase measurements are used for monitoring metastatic carcinoma of the prostate serum levels.
3 Acid Phosphatase - Some acid phosphatase is released into the circulation when the prostate is examined per rectum (P.R) and blood should be taken before this examination. - Serum acid phosphatase may be increased through nonprostatic causes, these include haemolysis, bone disease, particularly Paget's disease and metastatic carcinoma of the breast.
4 Acid Phosphatase Prostate-Specific Antigen - Prostate-specific antigen (PSA) found in prostatic tissue and is raised in serum in a higher proportion in cases of metastatic carcinoma than acid phosphatase - It is a more sensitive but less specific indicator of metastatic prostatic carcinoma.
5 Alkaline Phosphatase -Alkaline phosphatase is found in liver, bone, intestine, placenta and kidney, the main sources of serum enzyme are the hepatobiliary tree and osteoblasts. -Physiologically increased levels are seen during periods of active bone growth, particularly in infants and at puberty.
6 Alkaline Phosphatase -Values increase during the second and third trimesters of pregnancy to about twice those normally seen in adults. - Pathologically increases in serum alkaline phosphatase occur mainly in hepatobiliary disease and bone disease.
7 Alkaline Phosphatase - To identify the tissue of origin by determining alkaline phosphatase isoenzymes or by estimating the activity of another enzyme, usually Gamma- glutamyl transferase, which rises in parallel with biliary alkaline phosphatase.
8 Alkaline Phosphatase - Alkaline phosphatase activity in serum is usually estimated to detect increased levels, but markedly reduced levels are found in the inherited condition (hypophosphatasia), which is caused by defective bone calcification.
9 Transaminases Aspartate Aminotransferase - Aspartate aminotranferase (AST) is widely distributed, the heart, liver, skeletal muscle and kidney being rich sources. - Smaller amounts are found in erythrocytes and slight increases can occur in haemolysis.
10 Transaminases Aspartate Aminotransferase - The major diagnostic applications are in the investigation of myocardial infarction, liver disease and muscle disease.
11 Transaminases Alanine Aminotransferase - Alanine aminotransferase (ALT) is also widely distributed, the largest amounts occur in liver.
12 Transaminases Alanine Aminotransferase - Smaller amounts occur in the heart and ALT usually remains normal following myocardial infarction unless congestive cardiac failure occurs, causing release from the liver. - ALT is more specific for liver disease than AST.
Abnormalities of AST and ALT in various disease states Skeletal Muscle Injury AMICHFHepatitisCirrhosisBiliary Obstruction AST↑ or ↑↑ ↑↑↑↑↑ ALT→→↑ or ↑↑↑↑↑↑↑ 13
14 Gamma-glutamyl Transferase -Gamma-glutamyl transferase (GGT) is found in several tissues, the kidney being the richest source. - Significant amounts are present in the liver and pancreas, the major diagnostic application of GGT measurements in the investigation of hepatobiliary disease.
15 Gamma-glutamyl Transferase -Elevations in serum levels (70-80%) of patients who abuse alcohol, with more marked elevations occurring in the presence of alcoholic liver disease. -Gamm-glutamyl transferase is a less sensitive indicator of hepatocellular disease than transaminases but high serum levels occur in cholestasis.
16 Gamma-glutamyl Transferase - Serum GGT activity sometimes increases following myocardial infarction and in congestive cardiac failure, this is probably due to hepatic congestion.
Amylase -Amylase is a digestive enzyme, hydrolyzes glycosidic bonds in polymers of glucose, such as starch and glycogen, to produce maltose and other polysaccharides and dextrins. -Amylase is produced by the pancreas and salivary glands and its main diagnostic application is in the investigation of acute abdominal pain. 17
18 Amylase -The main source of elevated serum amylase activity is the pancreas. -Conditions causing increased levels of amylase: o Pancreatitis o Renal insufficiency o Ovarian malignancy o Ectopic pregnancy o Salpingitis o Lung carcinoma o Cardiac surgery o Mumps
19 Amylase -Serum amylase activities greater than 10 times the upper limit of normal are diagnostic of acute pancreatitis. -Elevated amylase activity may also be due to macroamylasemia (amylase is bound to immuno- globulin typically IgG in serum). -Patients with macroamylasemia evaluated using amylase:creatinine clearance ratio (ACCR). -The ACCR is typically increased in acute pancreatitis.
Lipase -Lipase is also a digestive enzyme secreted by the pancreas. -Catalyzes the hydrolysis of ester bonds in triglycerides to produce fatty acids and 2- acylglycerol. -Lipase along with amylase is utilized in the diagnosis of pancreatitis. -In the past, amylase was the test of choice for the diagnosis of pancreatic disease. 20
Lipase -Lipase is now considered to be more sensitive and specific than amylase as a marker of pancreatitis. -In patient with acute pancreatitis, lipase increased sooner and usually remains elevated for a longer period of time compared to amylase. -Pancreatic lipase has at least three isoforms. -Lipase isoforms provide more accurate diagnostic information than the measurement of total enzyme activity. 21
Lipase -Lipase in the peripheral circulation is removed via glomerular filtration and is completely reabsorbed by proximal tubule and not normally excreted in urine. -In patient with acute pancreatitis, lipase value > 10 times the upper limit of the reference interval and characterized as being pathogenic for the disease. 22
23 Cholinesterase Two types of cholinesterase are found in man: Acetylcholinesterase (AChE) also referred to as: true or RBC cholinesterase Serum cholinesterase (SChE) also referred to as: –Pseudocholinesterase or –Acylcholin acylhydrolase
Tissues Containing the Cholinesterases AChE: o Nervous system o Erythrocytes o Lungs o Spleen SChE: o Serum o Heart o Liver o Pancrease 24
25 Cholinesterase Cholinesterase Deficiency -Cholinesterase is synthesized in the liver and serum levels are often low in hepatic disease. - Organophosphorus insecticides, which are used in sheep dips, inhibit both cholinesterases and serum cholinesterase can be used to screen for poisoning.
26 Creatine Kinase -CK catalyses the phosphorylation of creatine. - The richest source of the enzyme is skeletal muscle while cardiac muscle and brain.
Tissues Containing Highest Levels of CK o Skeletal muscle o Cardiac muscle o Brain o Smooth muscle of the colon o Small intestine o Uterus o Prostate o Lungs o Kidneys 27
Conditions Causing a Marked Elevation in Total CK Activity o Acute myocardial infarction o Muscular dystrophy o Intramuscular injection o Pregnancy o Strenuous exercise o Surgery o Trauma o Myopathies o Hypothyroidism o Neoplastic disorders of the prostate,gastrointestinal tract,or bladder 28
29 Creatine Kinase - The main diagnostic application of CK is in the investigation of muscle disease, when the major circulating isoenzyme is CK-MM, and myocardial infarction, in which CK-MB predominates.
30 Lactate Dehydrogenate - Most tissues contain LDH and therefore measurements of the enzyme have low specificity. - LD composed of combination of two subunits designated H (heart) amd M (muscle), this may be improved by determining isoenzymes; five forms occur, the proportions of which vary between tissues.
Tissue Specificities of the LD Isoenzymes Predominant isoenzymes in myocardium and erythrocytes - LD-1 (HHHH) - LD-2 (HHHM) Predominant isoenzymes in lungs and spleen - LD-3 (HHMM) - LD-4 (HMMM) Predominant isoenzymes in liver and skeletal muscle - LD-5 (MMMM) 31
32 Lactate Dehydrogenate -Isoenzymes can be determined by electrophoresis which separates different forms on the basis of their electrical charge, heart having a high proportion of fast-moving enzyme, while the least mobile form predominates in liver. - The main diagnostic application of LDH measurements is in the investigation of myocardial infarction.
33 Lactate Dehydrogenate -LDH catalyses the reversible oxidation of L- lactate to pyruvate but also has activity against other hydroxy- and keto-acids, including hydroxybutyrate (2-oxobutyrate). - The cardiac isoenzyme has a high affinity for this substrate, while liver LDH reacts with it very slowly; therefore, the cardiac isoenzyme may be determined by measuring hydroxybutyrate dehydrogenase (HBD) activity.