A Cysteine Desulfhydrase Specific for ᴅ-Cysteine from the Green Alga Chlorella fusca

Abstract

A cysteine desulfhydrase was purified 110-fold from the green alga Chlorella using conven­tional techniques. The isolated cysteine desulfhydrase was specific for ᴅ-cysteine having no activity towards ʟ-cysteine. ᴅ- and ʟ-cysteine desulfhydrase activities can be separated using DEAE-cellulose chromatography techniques. The isoelectric point of this enzyme was deter­mined to be around a pH of 4.5 using a chromatofocussing column. The pH-optimum for the ᴅ-cysteine desulfhydrase was found to be in the range of 8.5 to 9 and the apparent Kᴍ for ᴅ-cysteine was determined to 0.16 mᴍ. The enzyme was active without addition of metal ions and EDTA or citric acid did not inhibit this activity.