Serum esterase genetics in rabbits. I. Phenotypic variation of the prealbumin esterases and classification of atropinesterase and cocainesterase.

Rabbit atropinesterase and cocainesterase were studied by starch gel electrophoresis. The enzymes are localized in a region of the gels anodal to the albumins (prealbumin esterases). In this region, three groups of esterase zones ( S, F, and D) can be distinguished. The S and F zones are almost exclusively responsible for the hydrolysis of cocaine and atropine, respectively. There is an interdependence of the S, F, and D zones: the activity of zone D depends on the presence of the three F zones, whereas these F zones are found only in combination with the three S zones, o~-Naphthylacetate as a substrate reveals six different phenotypes; two of these phenotypes are shown to be composed of two subtypes when a supplementary staining procedure is executed. A tropinesterase and cocainesterase are classified as carboxylesterases (E.C. 3.1.1.1.) with a rather wide specificity for both aliphatic and aromatic esters. The ~-naphthol esters are split better than the corresponding fl-naphthol esters. Naphthol esters with an acyl side-chain of three carbon atoms are hydrolyzed optimally by the enzymes.