Interstrain variation of esterase-22, a new isozyme of the house mouse.

1. A new liver esterase in the house mouse, ES-22, is described, using different staining methods after dose electrophoretic separation on polyacrylamide gels. 2. Five different phenotypes, ES-22A to ES-22E, could be distinguished in various mouse strains. ES-22 is genetically closely linked to ES-6, ES-9 and ES-20 on chromosome 8, but its distribution among different strains appears to be independent from these isozymes. 3. ES-22 is clearly different from other chromosome 8-controlled esterases, with respect to its organ expression and its catalytic properties. 4. A gene locus Es-22 with five alleles is suggested. 5. It is proposed that the genes coding for the carboxylesterase isozyme system on chromosome 8 constitute a multigene family as defined by Hood et al. (1975).