The reduction of trimethylarsine oxide by Candida humicola

Can J Microbiol. 1981 Aug;27(8):773-8. doi: 10.1139/m81-120.


Trimethylarsine oxide, a probable intermediate in the biological transformation of arsenate, was reduced to volatile trimethylarsine by Candida humicola. A simple assay for the rate of trimethylarsine production from trimethylarsine oxide by the fungus was developed. The optimum pH for the reduction was determined as 5.1-5.2, and the optimum temperature was 40 degrees C. The rate of reduction was directly proportional to cell concentration and followed Michaelis-Menten type kinetics. There was almost no trimethylarsine produced by heated or broken cells. The reaction was inhibited by a number of electron transport inhibitors and uncouplers of oxidative phosphorylation including cyanide, azide, and 2,4-dinitrophenol. The rate of reduction was modified by arsenate, methylarsonate, dimethylarsinate, selenate, and tellurate. Preincubation of cells with trimethylarsine oxide increased the rate of reduction 69-fold; this increase in activity was blocked if the cells were incubated with the protein synthesis inhibitor cycloheximide.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arsenicals / biosynthesis*
  • Candida / metabolism*
  • Cycloheximide / pharmacology
  • Electron Transport
  • Hydrogen-Ion Concentration
  • Kinetics
  • Oxidation-Reduction
  • Oxidative Phosphorylation
  • Temperature


  • Arsenicals
  • Cycloheximide
  • trimethylarsine