The isozymes of serum cholinesterase are shown to be interconvertible. Concentration of the individual isozymes results in an electrophoretically slower functional enzyme unit, whereas dilute solutions result in functional units with greater mobility. Since each of the four most mobile isozymes when isolated is convertible to the major isozyme form and each slower isozyme when isolated can be converted into the more mobile forms, this sequence is most likely stepwise in nature. The results indicate that the isozymes of serum cholinesterase are a manifestation of a polymerization sequence.

No abstract

No abstract

Intra-individual variation of serum cholinesterase activity as determined in 82 normal adults studied 373 times over periods up to 5 years is found to be relatively low. The over-all coefficient of variation was 8.4, the linear correlation between the first and subsequent tests in the same person was r = .87 (first versus second test in 82 subjects) and r = .90 (first versus seventh test in 14 people). A decline of 0.66 U. from a single prior measurement when in normal health is significant at the .05 level. The clinical significance of the test is discussed.

A method has been developed for demonstrating atypical serum cholinesterase by means of the self-indicating substrate, o-nitrophenylbutyrate and the inhibitor succinyldicholine. The procedure was tested for atypical cholinesterase with 76 individuals, including 5 otherwise proven homozygotes and their immediate families. In all cases, it was possible to distinguish clearly those individuals homozygous for the usual and atypical cholinesterase as well as heterozygotes.