1887

Abstract

SUMMARY: In previous work it had been shown that wild-type strain NCIB 8250 had only an L-mandelate deydrogenase but it could give rise to mutants that contained an evolved D-mandelate dehydrogenase; conversely, wild-type strain EBF 65/65 had only a D-mandelate dehydrogenase but gave rise to mutants that possessed an evolved L-mandelate dehydrogenase. Several other wild-type strains of have now been shown to grow on both enantiomers of mandelate. In every case the L-mandelate dehydrogenases were found to be much more heat-stable and insensitive to inhibition by -chloromercuribenzoate than were the D-mandelate dehydrogenases when measured in bacterial extracts. All the D-mandelate dehydrogenases in the wild-type strains were inactivated to about the same extent by an antiserum that had been raised in a rabbit against an evolved D-mandelate dehydrogenase. An evolved D-mandelate deydrogenase (from a mutant strain derived from strain NCIB 8250) and an original D-mandelate dehydrogenase (from a mutant strain derived from strain EBF 65/65) were purified to homogeneity by the same procedure and were indistinguishable as judged by immunological cross-reactivity of the native and the sodium-dodecyl-sulphate-denatured enzymes, solubility in cholate, net charge at pH 7.5, pI value, salting-out properties, value, apparent value for D-mandelate, heat-stability and sensitivity to -chloromercuribenzoate. The most likely explanation for the appearance of evolved mandelate dehydrogenases in strains of is that cryptic genes become expressed.

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/content/journal/micro/10.1099/00221287-134-4-967
1988-04-01
2019-11-18
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