Pyrrolysine is the 22nd naturally occurring genetically encoded amino acid used by some archaea (prokaryotic [lacking a membrane bound nucleus] and single-celled microorganisms) in enzymes that are part of their methane-producing metabolism. This lysine derivative is encoded by the UAG codon, normally a stop codon, possibly modified by the presence of a specific downstream sequence forcing the incorporation of pyrolysine instead of terminating translation.
| Micromole per liter | µmol/L = mcmol/L = umol/L = µM/L = mcM/L = uM/L = micromol/L |
| Milligram per liter | mg/L = millig/L = milligram/L = mg/liter |
| Milligram per deciliter | mg/dL = millig/dL = milligram/dL |
| Milligram per 100 milliliters | mg/100mL = millig/100mL = milligram/100mL |
| Milligram percent | mg% = millig% = milligram% |
| Microgram per milliliter | µg/mL = mcg/mL = ug/mL = microg/mL = microgram/mL |