Assay of DNA photolyase activity in spinach leaves in relation to cell compartmentation-evidence for lack of DNA photolyase in chloroplasts

Spinach cyclobutane pyrimidine dimer (CPD)-specific DNA photolyase was succ essfully detected in leaf extracts by an assay system for plant photolyase using an improved enzyme-linked immunosorbent assay (ELISA) which was newly introduced by novel horseradish peroxidase (HRP)-linked CPD specific monoc lonal antibodies. The assay system includes two main steps: a photorepair r eaction of CPD introduced in substrate DNA and measurement of CPD remained after the photorepair by the improved ELISA. When CPD-induced salmon sperm DNA was used as a substrate, high CPD-photolyase activities were observed i n the enzyme fraction prepared from whole spinach leaf extracts, but not fr om chloroplast extracts. This strongly suggests that spinach CPD-specific p hotolyases are localized in cell compartments other than chloroplasts.