geranylgeranyl diphosphate reductase activity
Catalysis of the reaction: phytyl diphosphate + 3 NADP+ = geranylgeranyl diphosphate + 3 NADPH + 3 H+. This enzyme also catalyzes the reduction of geranylgeranyl-chlorophyll a into phytyl-chlorophyll a.
GO:0016628
oxidoreductase activity, acting on the CH-CH group of donors, NAD or NADP as acceptor
is_a