Enzyme
ENZYMES
- Catalyzes reaction
DEFINITION OF TERMS
- Apoenzyme: protein portion of enzyme without cofactor
- Holoenzyme: complete active enzyme
- Active site: site where enzymatic reaction occurs
- Allosteric site: site other than the active site
- Isoenzyme: forms of enzyme that are different from each other but still
catalyzes same reaction
CATEGORIES
1. Oxidoreductase
- For oxidation/reduction reactions
- Ex: LDH, G6PD and Malate dehydrogenase
2. Transferase
- Catalyzes transfer of groups from one substrate unto another
- Ex: AST, ALT, CK, GG
3. Hydrolase
- Hydrolysi
- Ex: ACP, ALP, 5’NT, AMS, LPS, CHS
4. Lyase
- Removal of groups but with no hydrolysis
- Ex: Aldolas
5. Isomerase
- Interconversion of isomers
6. Ligase
- Joins to 2 substrate molecules
- Ex: synthases
| ENZYME | METHODS | SUBSTRATES | FACTS |
| HEPATIC ENZYME PROFILE | |||
| ALP Liver Kidney Bone Placenta Intestine WBC | Bodansky Shenowara Jones King-Armstrong Bessy Lowry-Brock | Β-glyceroPO4 Β-glyceroPO4 p-nitrophenylPO4 p-nitrophenylPO4 | Optimum pH: 10 Greatly elevated in Paget’s disease Avoid using EDTA-Citrate Oxalate |
| ALT (SGPT) Liver RBCs | Reitman-Frankel (DNPH) | Alanine α-keto | Liver-specific Marked elevation with viral hepatitis De ritis ratio: >1 = viral; <1 = non-viral |
| LD All tissues | Wacker Method (forward) Wrobleuski La Due (reverse) Wrobleuski Cabaud Berger Broida | NAD+ (cofactor) LD4 and LD5 Storage: 25°C upto 24 hours | |
GGT Canaliculi of | SZAZ | Gammaglutamyl p-nitroanilide | Most sensitive marker for alcoholic hepatitis |
| ChE | Pseudo- Michael; Ellman | Acetylcholine | ChE: CNS, RBC, Lungs, Spleen Pseudo: Liver – Succinylcholine (relaxant); anesthetic poisoning |
| CARDIAC ENZYME PROFILE | |||
| CK Cardiac, skeletal and brain tissues | Tanzer-Gilvarg (forward) Oliver-Rosalki (reverse) | CK-BB (fastest migrating; most anodal), CK-MB, CK MM (slowest; least anodal) Sensitive indicator of AMI & Duchenne disorder Highest elevation of total CK: Duchenne’s muscular dystrophy Light and pH sensitive | |
| AST (SGOT) Liver, heart, skeletal muscle | Karmen Method (Ph 7.5; 340 nm) | Aspartate α-keto | Most sensitive enzyme for skeletal muscle disease Inhibited by all anticoagulants except heparin (but ammonium heparin should not be used) |
| LD All tissues | Wacker Method (forward) – pH 8.8 Wrobleuski La Due (reverse) – pH 7.2 Wrobleuski Cabaud Berger Broida | LD1 (anodic & heat stable) LD2 (heat stable & major isoenzyme in the sera of healthy persons) LD5 (cathodic & cold labile) Flipped ratio: LD1>LD2 LD/HBD(LD1) ratio: 1.2-1.6; if 0.8-1.2 suspect for MI | |
| Myoglobin | Responsible for O2 supply of striated muscle | ||
| Troponin | 3 subunits: I (inhibitory), T (tropomyosin-binding) & C (calcium-binding) | ||
| ACUTE PANCREATITIS PROFILE | |||
| AMS Salivary glands, Pancreas | Saccharogenic Iodometric/Amyloclastic Chromogenic Kinetic Method | Pancreatic AMS: diastase Salivary AMS: ptyalin | MicroAMS: unbound (free) MacroAMS: bound to IgG and IgA Earliest pancreatic marker Smallest enzyme in size Salivary AMS: inhibited by wheat germ lectin |
| LPS Pancreas | Cherry-Crandall Sigma-Tietz Titration | Olive Oil/Triolein (pure form of TAG) | End product: Fatty Acids Most specific pancreatic marker |
| PROSTATIC CANCER PROFILE | |||
| ACP RBC Prostate | Chemical Inhibition Test RBC-ACP: inactivated by Cu++, unaffected by Tartrate P-ACP: unaffected by Cu++, inactivated by Tartrate | Organophosphates | Very labile (add 5M acetate buffer/citrate tablet to preserve) |
| PSA | Most useful for tumor marker for prostate cancer RR: 0-4ng/mL | ||
| ACUTE MYOCARDIAL INFARCTION MARKERS (Bishop, Rodriguez, Coderes) | |||
| Marker | Onset (hrs) | Peak (hrs) | Duration (hrs) |
| Myoglobin | 1-3 | 5-12 | 18-30 |
| Trop I | 3-4 | 10-24 | 7days up to 10-14days |
| Trop T | 3-6 | 12-18 | 5-10 days |
| CK-MB | 4-6 | 12-24 | 48-72 |
| AST | 6-8 | 24 | 5 days |
| LDH | 12-24 | 48-72 | 10-14 days |
