CHARACTERIZATION OF CHLOROPHYLL-A AND BACTERIOCHLOROPHYLL A SYNTHASESBY HETEROLOGOUS EXPRESSION IN ESCHERICHIA-COLI

Genes coding for putative chlorophyll a synthase (chlG) from Synechocy stis sp, PCC 6803 and bacteriochlorophyll a synthase (bchG) from Rhodo bacter capsulatus were amplified by the polymerase chain reaction and cloned into T7 RNA polymerase-based expression plasmids, In vitro enzy matic assays indicated that heterologous expression of the chlG and bc hG gene products in Escherichia coli conferred chlorophyll a and bacte riochlorophyll a synthase activity, respectively, Chlorophyll a syntha se utilized chlorophyllide a, but not bacteriochlorophyllide a, as a s ubstrate, whereas bacteriochlorophyll a synthase utilized bacteriochlo rophyllide a, but not chlorophyllide a. Both enzymes were also observe d to exhibit a marked preference for phytyl diphosphate over geranylge ranyl diphosphate.