ID 2.5.1.133 DE bacteriochlorophyll a synthase. CA bacteriochlorophyllide a + (2E,6E,10E)-geranylgeranyl diphosphate + H(+) CA = geranylgeranyl-bacteriochlorophyllide a + diphosphate. CC -!- The enzyme catalyzes the addition of a geranylgeranyl hydrophobic CC chain to bacteriochlorophyllide a via an ester bond with the CC 17-propionate residue. CC -!- The side chain is later modified to a phytyl chain, resulting in CC bacteriochlorophyll a. //