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6150161 
Book/Book Chapter 
[43] Rhodanese: CN−+S2O3−−→ CNS−+SO3−− 
Sörbo, BH 
1955 
1 
Methods in Enzymology
ISSN: 0076-6879
EISSN: 1557-7988 
Academic Press 
Methods in Enzymology 
2 
334-337 
Publisher Summary This chapter discusses the rhodanese. The assay method is based on the colorimetric determination of the thiocyanate formed in the reaction. The red color obtained in the presence of ferric ions is conveniently used for this purpose. The appearance of an interfering blue color (due to an iron-thiosulfate complex) is prevented in the present method by the presence of formaldehyde. The method given here is applicable to rhodanese preparations of any degree of purity. One rhodanese unit (R.U.) is defined as that amount of enzyme which forms 10 microequivalents of thiocyanate under the above conditions. Specific activity is expressed as rhodanese units per milligram dry weight. With purified enzyme preparations protein is determined according to Bücher instead of the dry weight. The steps described in the purification procedure are extraction, fractionation with ammonium sulfate at pH 3.8, fractionation with ammoniacal ammonium sulfate, dialysis, acetone fractionation, dialysis, ammonium sulfate fractionation at pH 4.5, and crystallization.