-Prelim LEC Lesson 3 AST ALT ACP ALP.pdf

LIVER ENZYMES ▪ AST ▪ ALT  Aspartate Aminotransferase Alanine Aminotransferase ▪ E.C. 2.6.1.1 ▪ E.C. 2.6.1.2 ▪ L-Aspartate: 2-oxaloglutarate ▪ L-Alanine: 2-oxaloglutarate Aminotransferase...

LIVER ENZYMES ▪ AST ▪ ALT  Aspartate Aminotransferase Alanine Aminotransferase ▪ E.C. 2.6.1.1 ▪ E.C. 2.6.1.2 ▪ L-Aspartate: 2-oxaloglutarate ▪ L-Alanine: 2-oxaloglutarate Aminotransferase Aminotransferase ▪ Transfer of an amino group between aspartate and alpha-keto ▪ Transfer of an amino group between acids to form oxaloacetate and alanine and alpha-keto acids to form glutamate glutamate and pyruvate – Former name: – Former name: ▪serum glutamic-oxaloacetic ▪ serum glutamic-pyruvic transaminase (SGOT or GOT) transaminase (SGPT or GPT) – Cofactor: – Cofactor: ▪Pyridoxal phosphate (Vit. B6) ▪ Pyridoxal phosphate (Vit. B6) ASPARTATE AMINOTRANSFERASE (AST) ▪ Functions in the synthesis and degradation of amino acids ▪ Ketoacids formed are ultimately oxidized by the tricarboxylic acid cycle to provide a source of energy  Aspartate Aminotransferase Alanine Aminotransferase Tissue Sources Tissue Sources – Liver – highest – Cardiac tissue – highest – Kidney – Liver – Heart – Skeletal muscles – Skeletal muscle – Kidney – Pancreas – Pancreas – Spleen – Erythrocytes – Erythrocytes Intracellular level: 7000 times than plasma – Intracellular level: 3000 times than plasma  ASPARTATE AMINOTRANSFERASE (AST) Isoenzyme Fractions – Cell cytoplasm ▪ Predominant form in serum – Mitochondria ▪ Increased in disorders producing cellular necrosis  ASPARTATE AMINOTRANSFERASE (AST) Diagnostic Significance – Limited mainly to the evaluation of hepatocellular disorders and skeletal muscle involvement – AMI ▪ Rise: 6 – 8 hours ▪ Peak: 24 hours ▪ Normalizes within 5 days – Not useful in the diagnosis of AMI  ASPARTATE AMINOTRANSFERASE (AST) Diagnostic Significance – Pulmonary embolism – Congestive heart failure – Acute Hepatocellular Disorders – Viral Hepatitis: 100 times ULN – Liver cirrhosis: 4 times ULN – Muscular Dystrophy: 4-8 times ULN – Inflammatory conditions  ALANINE AMINOTRANSFERASE (ALT) Diagnostic Significance – Confined mainly to the evaluation of hepatic disorders (hepatocellular disorders): ALT elevation is frequently higher than AST due to its longer half-life in the blood (47 hours vs. 17 hours) Note: In acute hepatocellular injury, initially AST > ALT but ALT > AST within 24-48 hours (except in alcohol-induced hepatocyte injury which damages the mitochondria; mitochondrial AST has a half-life of 87 hours; De Ritis ratio: 3-4: 1)  PHOSPHATASES Alkaline phosphatase Acid phosphatase ▪ Catalyze the hydrolysis of various phosphomonoesters at a certain pH ▪ Liberate inorganic phosphate from an organic phosphate ester with the concomitant production of an alcohol  Alkaline Phosphatase Acid Phosphatase ▪ E.C. 3.1.3.1 ▪ E.C. 3.1.3.2 ▪ Orthophosphoric Monoester ▪ Orthophosphoric Monoester Phosphohydrolase (Alkaline Phosphohydrolase (Acid Optimum) Optimum) ▪ Optimum pH: 9.0 - 10.0 ▪ Optimum pH: 5.0 ▪ Cofactor: Magnesium and ▪ Cofactor: Magnesium and Zinc Zinc  Alkaline Phosphatase Acid Phosphatase Tissue Sources Tissue Sources ▪ Present on the cell surfaces ▪ Prostate – richest source of most tissues ▪ Bone – Liver ▪Sinusoidal and bile canalicular ▪ Liver membranes ▪ Spleen – Bone: Osteoblasts – Intestine ▪ Kidney – Spleen ▪ RBC – Placenta ▪ Platelets – Kidney  ALKALINE PHOSPHATASE (ALP) Four Major Isoenzymes ▪ Placental ALP ▪ Liver ALP ▪ Bone ALP Intestinal ALP (common in pxs with Blood Type B or O and are secretors)  Methods used to differentiate the isoenzymes and other multiple forms of ALP: – Electrophoresis – Stability to denaturation by heat or chemicals – Response to the presence of selected inhibitors – Affinity for specific lectins – Immunochemical characteristics  ALKALINE PHOSPHATASE (ALP) Isoenzymes (Electrophoresis) – Liver ALP: migrates the fastest and most anodal ▪ Major liver fraction: usually in the early stages of hepatobiliary conditions ▪ Fast liver fraction (Alpha1 liver): found in metastatic carcinoma of the liver and hepatobiliary diseases (valuable indicator of obstructive liver disease) – Bone ALP: osteoblast activity – Placental ALP – Intestinal ALP  ALKALINE PHOSPHATASE (ALP) Isoenzymes (Heat Stability) – ALP activity is measured before and after heating the serum at 56 degrees Celsius for 10 minutes ▪ Placental ALP: Most heat stable (resist heat denaturation at 65ºC for 30 min) ▪ Intestinal ALP ▪ Liver ALP ▪ Bone ALP  ALKALINE PHOSPHATASE (ALP) Isoenzymes (Heat Stability) – If the residual activity after heating is less than 20% of the total activity before heating – Bone ALP – Greater than 20% - Liver ALP – Alternative: use of neuraminidase and wheat germ lectin  ALKALINE PHOSPHATASE (ALP) Isoenzymes (Chemical Inhibition) ▪ Impossible to differentiate the four fractions ▪ Phenylalanine – Inhibits intestinal ALP and placental ALP to a much greater extent than liver and bone ALP ▪ Levamisole – Inhibits bone ALP and liver ALP (Henry) ▪ 3M Urea – Inhibits bone ALP  ALKALINE PHOSPHATASE (ALP) Isoenzymes (Abnormal Fractions associated with Neoplasms): ectopic production of an enzyme by malignant tissues – Regan Isoenzyme – Nagao Isoenzyme – Kasahara isoenzyme: hepatocellular/gastric/maxillary/pulmonary/bladder carcinoma ▪ Carcinoplacental Alkaline Phosphatases – Similarities to the placental isoenzyme – 3% to 15% in cancer patients  ALKALINE PHOSPHATASE (ALP) ▪ Regan Isoenzyme – Detected in various carcinomas ▪ Increased in ovarian (highest incidence) and gynecologic cancers (better used as therapy monitor) – Most heat stable of all ALP: resists denaturation (65 degrees Celsius for 30 minutes) – inhibited by phenylalanine and migrates like bone ALP  ALKALINE PHOSPHATASE (ALP) ▪ Nagao Isoenzyme – Identical to the Regan fraction (considered as a variant of Regan) – Inhibited by both phenylalanine and L-leucine – Detected in metastatic carcinoma of pleural surfaces and adenocarcinoma of the pancreas and bile duct  ALKALINE PHOSPHATASE (ALP) Diagnostic Significance – HEPATOBILIARY DISORDERS ▪ Biliary Tract Obstruction: 3 – 10 times ULN due to increased synthesis of the enzyme induced by cholestasis (translocation of ALP to the sinusoidal surface) – HEPATOCELLULAR DISORDERS ▪ Hepatitis and cirrhosis (usually less than 3 times ULN)  CHOLESTASIS Failure of bile excretion or transport Extrahepatic Gall stones (cholelithiasis and choledocholithiasis) Cysts and carcinoma Parasitic infection Intrahepatic Viral hepatitis Cholestasis in pregnancy (due to estrogen) May lead to cholangitis (inflammation of the bile duct) Hallmarks: Charcot’s triad/Reynold’s pentad (Tokyo Guidelines are also used)  ALKALINE PHOSPHATASE (ALP) Diagnostic Significance – Bone Disorders ▪ Paget Disease (osteitis deformans): gain in bone mass (disordered/unsound new bone) ▪ Osteomalacia and rickets ▪ Hyperparathyroidism ▪ Osteogenic carcinoma ▪ Healing bone fractures ▪ During periods of physiologic bone growth  ALKALINE PHOSPHATASE (ALP) Diagnostic Significance – Normal Pregnancy ▪ Increased ALP ▪ Can be detected between weeks 16 and 20 and persists until the onset of labor ▪ May be elevated in hypertension, preeclampsia, and eclampsia, threatened abortion  ALKALINE PHOSPHATASE (ALP) Diagnostic Significance –Decreased ALP is observed in hypophosphatasia (an inborn error of metabolism) – Defect in the gene that encodes for ALP isoenzymes (kidney, liver, bone)  ACID PHOSPHATASE (ACP) Isoenzymes ▪ Prostatic ACP – inhibited by tartrate (Total ACP– ACP after tartrate inhibition) ▪ Red cell / Erythrocyte ACP – inhibited by 2% formaldehyde and 1mmol cupric sulfate ▪ TRAP (Abnormal fraction): marker for hairy cell leukemia – TRAP-5b :produced by osteoclasts in the bone marrow and is used as a marker for bone remodeling/resorption  ACID PHOSPHATASE (ACP) Diagnostic Significance ▪ has been used as an aid in the detection of prostatic carcinoma, particularly metastatic cancer of the prostate – Prostate-Specific Antigen ▪ more specific than ACP; useful in therapy monitoring ▪ May elevate in benign prostatic hypertrophy and prostatitis  ACID PHOSPHATASE (ACP) Diagnostic Significance ▪ Useful in investigation of rape: vaginal washings are examined for seminal fluid ACP activity, which can persist for up to 4 days ▪ Presumptive evidence of rape: ACP activity > 50 U/L = positive  ACID PHOSPHATASE (ACP) Diagnostic Significance ▪ Increased ACP – Bone disease – associated with osteoclasts – Paget disease – Breast cancer with bone metastases – Gaucher disease – caused by a deficiency of the enzyme glucocerebrosidase leading to the buildup of fatty substances in certain organs  ACID PHOSPHATASE (ACP) Diagnostic Significance ▪ Increased ACP ▪ Thrombocytopenia –Resulting from excessive platelet destruction from Idiopathic Thrombocytopenic Purpura (ITP)