UNIT 6.13 Methods for Measuring Cysteine S-Conjugate β-Lyase Activity

  1. Lawrence H. Lash

Published Online: 1 NOV 2007

DOI: 10.1002/0471140856.tx0613s34

Current Protocols in Toxicology

Current Protocols in Toxicology

How to Cite

Lash, L. H. 2007. Methods for Measuring Cysteine S-Conjugate β-Lyase Activity. Current Protocols in Toxicology. 34:6.13:6.13.1–6.13.22.

Author Information

  1. Wayne State University School of Medicine, Detroit, Michigan

Publication History

  1. Published Online: 1 NOV 2007
  2. Published Print: NOV 2007


The cysteine conjugate β-lyase represents activities in cytoplasm and mitochondria catalyzed by at least eleven pyridoxal 5′-phosphate (PLP)-dependent enzymes in various tissues. These enzymes mediate bioactivation of cysteine S-conjugates of several haloalkanes and haloalkenes. The reaction occurs through either a direct β-elimination or a transamination followed by a retro-Michael rearrangement, resulting in the cleavage of a C–S bond. The resultant product is a reactive thiolate that rearranges to form thioacylating species. This unit presents several protocols for the assay of β-lyase activity and includes measurements of product formation and substrate loss as well as fluorescent activity stains. Support protocols describe the synthesis and high-performance liquid chromatography analysis of selected cysteine S-conjugates. Because of the diversity of enzymes that can catalyze a β-lyase reaction, each of the assays presented here may indicate only a portion of the potential β-lyase activity in a given biological preparation. Curr. Protoc. Toxicol. 34:6.13.1-6.13.22. © 2007 by John Wiley & Sons, Inc.


  • glutathione conjugation pathway;
  • cysteine S-conjugate β-lyase;
  • β-elimination;
  • transamination;
  • aminotransferases;
  • glutamine transaminase K;
  • kynureninase;
  • reactive thiolate;
  • pyruvate;
  • spectrophotometric assays;
  • HPLC assays