| 5’ nucleotidase (5-NTD) | Key enzyme in nucleotide metabolism. Elevated levels are specific for liver cholestasis and hepatoma. |
| 6-phosphogluconate-dehydrogenase | Another important enzyme of the pentose phosphate shunt, produces NADPH |
| Acetylcholinesterase | Breaks down Acetilcholine (Ach) into choline and acetic acid, located in the postsynaptic membrane, so quickly reduces the amount of Ach from the synaptic cleft (neuro-muscular junction). Organophosphate compounds irreversibly inhibit AchE enzyme, causing extreme parasympathettic activity (remember "dummbbless" to recall the symptoms) |
| Acetyl-CoA carboxylase | Converts Acetyl CoA to Malonyl CoA (FA synthesis) |
| Acid phosphatase (ACP) | Prostate specific enzyme, level is elevated in prostatic carcinoma. |
| Adenylyl-cyclase | After a hormone binds its receptor and activates G protein, the adenylyl-cyclase enzyme converts ATP to cAMP (which is a second messenger) |
| alanine-aminotransferase (ALT) | Alanine + α-ketoglutarate ⇌ glutamate + pyruvate. Specific to liver cells, elevated in liver cell damage, such as acute hepatitis. (see also: transaminase) |
| Aldolase | One of the enzymes in glycolysis, splits fructose 1,6 bisphosphate into dihydroxyacetone phosphate (entry substrate of lipogenesis converted into glycerol) and glyceraldehyde-3-phosphate. Aldolase deficiency causes fructose intolerance. |
| Alkaline phosphatase (ALP) | Widely distributed in several tissues, but higher in placenta, adrenal gland, liver, and bone. Elevated ALP is indicative of biliary obstruction and bone cancer/metastasis (resorption). |
| Alpha-1,4 glucosidase | Group of enzymes, that can break the alpha 1,4- glycosidic bonds in starch and disaccharides and release alpha-glucose. Deficiency of this enzyme causes glycogen storage disease type II (normal structure glycogen, but the body can’t use it to produce glucose) |
| aspartate-aminotransferase (AST) | Aspartate + α-ketoglutarate ⇌ glutamate + oxaloacetate. Elevated in acute hepatitis, and muscle injury. (See also: transaminase) |
| Carbonic anhydrase | CO2 + H2O -> HCO3 -> CO2 + HCO3 |
| Catechol-O-methyltransferase (COMT) | Metabolites can be found in the urine: VMA (vanillyl-mandelic acid, and (nor)metanephrine. |
| Cholesterol esterase | Cholesteryl ester + H2O -> Cholestrol + Fatty Acid |
| creatine kinase (CK) | Creatine + ATP -> Phosphocreatine + ADP (storage of energy in muscle cells). |
| creatine kinase isoenzymes! | 2 subunits: MM, MB, BB (40x2=80 kDa), and atypical forms (macro-CK), located in the cytoplasm, cellular damage casues elevation of enzyme level in the blood. |
| Deaminase (glutamate dehydrogenase) | Catalyze deamination, which prepares amino acids for entry to Krebs cycle by removing ammonia. Tha ammonium ion enters the urea cycle. |
| DOPA decarboxylase | L- DOPA -> Dopamine |
| Dopamine β hydroxylase, | Dopamine -> Norepinephrine |
| Endopeptidase (pepsin, trypsin, chymotrypsin, elastase). Exopeptidase (carboxypeptidase, aminopeptidase). | Proteolytic enzymes. Endopeptidases break protein bonds inside the peptide chain. Exopeptidases act at the ends of the peptides. Pepsin is activated by HCL, trypsin activates other pancreatic enzymes (chymotrypsin, elastase, carboxypeptidase). |
| Galactokinase, | Galactose + ATP -> Galactose-1-phosphate. Deficiency of this enzyme causes Galactosemia type 2. |
| galactose-1-phosphate uridyl-transferase (GALT) | Galactose-1-phosphate + UTP -> UDP galactose +PPi, Deficiency of this enzyme causes Galactosemia type 1 (more severe). |
| Glucokinase/hexokinase | Enzyme that converts glucose into glucose-6-phosphate (first reaction of glycolysis, consumes 1 ATP). |
| Glucose-6-phosphatase | Converts glucose-6-phosphate into glucose (in liver cells, so liver is able to give away glucose to maintain serum glucose level, muscle cells lack this enzyme!) |
| Glucose-6-phosphate-dehydrogenase | Enzyme that converts glucose-6-phosphate into 6-phosphogluconate + NADPH (G6PD deficiency: X linked recessive, causes hemolysis in oxidative stress b/c increased level of the oxidized form of glutathione in RBCs) |
| Glucuronyl-transferase | Key enzyme of bilirubin metabolism, converts unconjugated bilirubin into conjugated bilirubin, called glucuronidation. |
| Glutathione-reductase | This enzyme keeps glutathione in reduced form (GSSG – GSH) in RBCs. Requires NADPH from pentose phosphate shunt! |
| Glycogen phosphorylase | This enzyme breaks down glycogen in a single enzymatic reaction – fast to provide glucose. [Glycogen into Glucose – 1- phosphate (glucose)] |
| Glycogen synthase | Synthesis of glycogen (liver, muscle) requires UDP. |
| HMG-CoA reductase | The main enzyme that is responsible for cholesterol synthesis. |
| Lactase, | Lactose to 1 galactose and 1 glucose |
| Lactate dehydrogenase (LDH) | Pyruvate -> Lactate (requires NADH) |
| Lactate dehydrogenase isoenzymes! | 5 isoenzymes (tetramer, combination of two diff PP chain: LDH 4H = heart, LDH 4M = muscle and liver) |
| Lecithin cholesterol acyltransferase (LCAT) | Converts free cholestrol to cholesteryl ester which can be added into lipoproteins. |
| Lipoprotein lipase | Acts on the endothelial surface of capillaries and breaks down triglycerides releasing fatty acids. |
| Maltase | Converts maltose to 2 glucose molecules. |
| Monoamine oxidase (MAO) | Catecholamine metabolism |
| Phenylalanine hydroxylase | Converts Phenylalanine to Tyrosine. Breaks down extra Phenylalanine, genetic deficiency of this enzyme causes Phenylketonuria. |
| Phenyl-ethanolamine N-methyltransferase | Norepinephrine -> Epinephrine |
| Phosphodiesterase (PDE) | Group of enzymes that inactivates cAMP by converting it back to AMP. (there are many drugs targeting PDE enzymes e.g. sildenafil inhibits PDE5, milrinone and dipyridamole inhibits PDE3) |
| Phosphokinase A (PKA) and C (PKC) | Phosphorylate enzymes/proteins, altering cell metabolism after hormonal activation. PKA associated with cAMP, PKC with Ca. |
| Phospholipase A2 | Forms arachidonic acid (AA) from membrane phospholipids, AA is the precursor of eicosanoid- and prostaglandin synthesis. PLA2 is a key enzyme in the inflammatory response. |
| Phospholipase-C | PIP2 -> IP3 + DAG (PIP2: Phosphotidylinositol 4,5-Bisphosphate, IP3: Inositol Triphosphate, DAG: Diacylglycerol) |
| Sodium - dependent glucose transporter | Secondary active transport, located in the intestinal mucosa and the proximal renal tubules transporting glucose into the cell, glucose is coupled to Na+ (cotransport). |
| Sodium-potassium exchange pump | Primary active transport, transporting 3 Na+ out of the cell, and 2 K+ into the cell. |
| Sucrase, | Sucrose to 1 glucose and 1 fructose |
| Thyroid-peroxidase | Thyroid hormone synthesis: Iodination of tyrosine, and conjugation of T2 and T1 to produce T3 and T4 |
| Transaminase (ALT, AST) | These enzymes transfer the amino group of an AA to a keto-acid. The ketoacid is converted into another AA. |
| Tyrosine hydroxylase, | L-Tyrosine -> L- DOPA |
| α-1,6-glycosidase | Isomaltose into 2 glucose |
| α-amylase, lipase | Pancreatic enzymes, alpha amylase hydrolyzes alpha 1,4 glycosidic linkages of complex carbohydrates |
| γ-glutamyl transferase (GGT) | Liver specific enzyme, elevated in alcoholic hepatitis, and hepatoma (cancer). |