An analysis of molecular polymorphism of esterase M produced by motileAeromonas strains

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Abstract
The high levels of electrophoretic polymorphism of esterase M detected in eight distinct hybridization groups of motileAeromonas raise questions of genetic homogeneity of the electromorphs. The 40 electromorphs detected fall in fourM r classes—75, 80, 90, and 110 kD—and one typical variant belonging to each of these classes was purified. The four purified esterases exhibited the same resistance to heat, topH and to diisopropyl fluorophosphate, the sameK m values for 1-naphthyl acetate and 1-naphthyl propionate (1mm), and immunological cross-reactions. Within each class, the electromorphs appeared to be related in term of single amino acid substitutions as estimated from their comparative titration patterns. The titration curves of the four purified esterases were strictly parallel suggesting close structural similarities. Thus, despite considerable variation in theirpI,M F,andM r values, it seems likely that the variants of esterase M are the products of closely related loci originating from a common ancestral gene.