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

A cysteine desulfhydrase was purified 110-fold from the green alga Chlorella using conven­ tional techniques. The isolated cysteine desulfhydrase was specific for D-cysteine having no activity towards L-cysteine. Dand L-cysteine desulfhydrase activities can be separated using DEAE-cellulose chromatography techniques. The isoelectric point o f this enzyme was deter­ mined to be around a pH o f 4.5 using a chromatofocussing column. The pH-optim um for the D-cysteine desulfhydrase was found to be in the range o f 8.5 to 9 and the apparent for D-cysteine was determined to 0.16 m M . The enzyme was active without addition o f metal ions and EDTA or citric acid did not inhibit this activity.