|paper : common FMO3 variants|
In the study they look to see how common the 3 missense variants at codons 158, 257, and 308 are among a group of Turks. FMO3 is made up of a 532 amino acid sequence (532 codons). A missense variant is where an incorrect amino acid is inserted. Normally this would make no difference in itself, however in combination with other missense codons it can result in loss of function to some degree.
Common variants at codons 158, 257, and 308
E158K missense variant
amino acid should be E but K is inserted
E & K are amino acid symbols
E is glutamic Acid
K is lysine
In the Turkish group in the study, it was found that 80% either were totally 'normal' at the codons 158,257,308 (ie 'EVE') or carried the 158 variant (KVE) but all would be predicted as having normal FMO3 function. That, therefore, leaves 20% with various combinations of the 3 variants. The various combinations do not mean they will definitely have some loss of function, but in some combinations, it can, and it makes it more likely.
Flavin-containing monooxygenase 3 gene polymorphisms in turkish population
FMO3 letter to editor 2000
TMAU article on NIH.gov website