Abstract
During the purification of Clp protease from chloroplast stroma of spinach, we found other enzyme that degrades Suc-Leu-Tyr-MCA, the substrate of Clp protease. This enzyme was purified by five steps of chromatography and molecular weight was estimated as 35,000. The N-terminal sequence of this protein was determined to be AVSLSPP and this sequence completely agreed with that of O-Acetylserine (thiol) lyase (OAS lyase) derived from the spinach chloroplast. OAS lyase is the last enzyme in the cysteine biosynthetic pathway. This enzyme distributes in cytosol, mitochondria, and chloroplast. The enzyme had an absorption peak at 407 nm due to the presence of pyridoxal phosphate, which is a cofactor of OAS lyase. Our purified enzyme also showed the absorption peak at 407 nm. From these results, it is likely to conclude that the purified enzyme that degrades Suc-Leu-Tyr-MCA is OAS lyase. Kinetical analysis of the enzyme is now in progress.
