| Enzyme Name | Gene Symbol | Functions |
| ALA dehydratase | ALAD | is the second enzyme in the pathway of heme biosynthesis, catalyzes the condensation of two molecules of δ-aminolevulinic acid (ALA) forming porphobilinogen |
| Alcohol dehydrogenases, ADH | 7 different genes | belong to medium-chain dehydrogenase/reductase (MDR) superfamily; catalyze the oxidation of various alcohols to their corresponding aldehydes; important in the detoxification/metabolism of ethanol |
| Aldolases | ALDOA, ALDOB, ALDOC | catalyzes the hydrolysis of fructose-1,6-bisphosphatase (ALDOA) in the pathway of glycolysis; ALDOB is involved in the hepatic metabolism of fructose |
| Alkaline phosphatase, ALP | ALPL, ALPP, ALPI, ALPPL2 | four different enzymes, three encoded by three different genes all clustered on chromosome 2, each of these three (ALPP, ALPI, ALPPL2) is tissue specific in expression, the non-tissue specific form of the enzyme is expressed from the ALPL gene on chromosome 1; each enzyme catalyzes the dephosphorylation of substrates in an alkaline environment; high amounts of ALP found in liver and bone; measurement for elevation in the blood is used in the overall diagnosis of liver or bone disease |
| Aspartate transcarbamoylase | CAD | a tri-functional enzyme that catalyzes the initial three rate-limiting reactions of pyrimidine nucleotide biosynthesis; the three activities are carbamoylphosphate synthetase 2, aspartate transcarbamoylase, and dihydroorotase |
| Carbonic anhydrases, CA | at least 12 different functional members | catalyze the formation of carbonic acid (H2CO3) from CO2 and H2O; see the Enzyme Kinetics page for more details |
| Histone deacetylases, HDACs | at least 18 different members of family | as the name implies, these enzymes remove acetyl groups from histones; the consequences of histone deacetylation are the silencing of transcription; the sirtuin (SIRT) proteins in humans also possess HDAC activity |
| Monoamine oxidases | MAOA, MAOB | catalyze the oxidation of monoamines; critical roles in the regulaiton of the catabolism of dopamine, serotonin, epinephrine, and norepinephrine; given these important functions MAO inhibitors (MAOIs) were used for several years as anti-depressants and anti-anxiety drugs; due to potential for excessive levels of epinephrine and norepinephrine MAOIs can cause hypertensive crisis |
| Phospholipase C (PLC) | 13 enzymes in family | PLCβ and PLCγ most well characterized members of the family; each enzyme hydrolyzes membrane phospholipids, primarily polyphosphoinositols, at the bond where the phosphate is attached to the glycerol backbone |
| Pyridoxal kinase | PDXK | required for the formation of the cofactor form of vitamin B6: pyridoxal phosphate (PLP; also identified as pyridoxal-5-phosphate) |
| Pyruvate carboxylase | PC | first of two enzymes required for bypass 1 step of gluconeogenesis; catalyzes the formation of oxaloacetate from pyruvate and bicarbonate ion |
| Superoxide dismutase, Cu-Zn | SOD1 | major cytoplasmic anti-oxidant enzyme; catalyzes conversion of superoxide free radicals to molecular oxygen (O2) or hydrogen peroxide (H2O2); the major mitochondrial superoxide dismutase (SOD2) is a manganese-dependent enzyme |
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