Mutations affecting a regulated, membrane-associated esterase in Salmonella typhimurium LT2

Mol Gen Genet. 1994 Jun 15;243(6):674-80. doi: 10.1007/BF00279577.


Mutations at the apeA locus in Salmonella typhimurium lead to loss of a soluble enzyme ("protease I") that hydrolyzes the chromogenic endoprotease substrate N-acetyl phenylalanine beta-naphthyl ester. We have isolated pseudorevertants of S. typhimurium apeA mutations that have regained the ability to hydrolyze this compound. These pseudorevertants contain mutations (apeR) that lead to overproduction of a membrane-bound esterase different from protease I. The apeR locus is phage P1 cotransducible with ilvC (83 map units) and is unlinked to apeA. Mutations at still another locus, apeE, lead to loss of the membrane-associated esterase. The apeE locus is P1 cotransducible with purE (12 map units). In an apeE-lacZ operon fusion strain, an apeR mutation increases the level of beta-galactosidase approximately 60-fold. We propose that apeR encodes a repressor of apeE. The evidence available suggests that the ApeE protein is not a protease.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Esterases / biosynthesis
  • Esterases / genetics*
  • Gene Expression Regulation, Bacterial*
  • Genes, Bacterial / genetics
  • Membrane Proteins / genetics
  • Mutation*
  • Phenylalanine / analogs & derivatives*
  • Phenylalanine / metabolism
  • Salmonella typhimurium / genetics*
  • Transcription, Genetic


  • Membrane Proteins
  • N-acetylphenylalanine beta-naphthyl ester
  • Phenylalanine
  • Esterases