Enzymatic synthesis of selenocysteine in rat liver

Biochemistry. 1981 Jul 21;20(15):4492-6. doi: 10.1021/bi00518a039.

Abstract

We have investigated selenocysteine (2-amino-3-hydroselenopropionic acid) synthesis with cystathionine beta-synthase (EC 4.2.1.22) and cystathionine gamma-lyase (EC 4.4.1.1) of rat liver. When selenohomocysteine and serine were incubated with cystathionine beta-synthase, selenocystathionine was formed at a rate of 69% of that of cystathionine synthesis. Cystathionine gamma-lyase catalyzed alpha, gamma elimination of selenocystathionine to yield alpha-ketobutyrate, selenocysteine, and NH3. The reaction rate was about 3 times higher than that of cystathionine elimination. Cystathionine beta-synthase, however, did not catalyze direct formation of selenocysteine from serine and H2Se. Thus, selenocysteine is synthesized from selenohomocysteine and cystathionine beta-synthase and cystathionine gamma-lyase reactions. We confirmed this synthetic pathway also with a mixture of both enzymes and with a homogenate of rat liver.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cystathionine beta-Synthase / metabolism*
  • Cystathionine gamma-Lyase / metabolism*
  • Cysteine / analogs & derivatives*
  • Cysteine / biosynthesis
  • Hydro-Lyases / metabolism*
  • Kinetics
  • Liver / enzymology*
  • Lyases / metabolism*
  • Mass Spectrometry
  • Rats
  • Selenium / biosynthesis*
  • Selenocysteine

Substances

  • Selenocysteine
  • Lyases
  • Hydro-Lyases
  • Cystathionine beta-Synthase
  • Cystathionine gamma-Lyase
  • Selenium
  • Cysteine