p.T243M Thr243Met (p.T271M Thr271Met in primary sequence with 28 amino-acids signal peptide) (from OMIM) Fluoride-resistant I, F-1 CHE*243M Harris and Whittaker (1961) described this variant which has a homozygote frequency of about 1:150,000. The fluoride variant of human butyrylcholinesterase owes its name to the observation that it is resistant to inhibition by 0.050 mM sodium fluoride in the in vitro assay. Individuals who are compound heterozygotes for the fluoride and atypical alleles experience about 30 min of apnea, rather than the usual 3-5 min, after receiving succinyldicholine.
