Phototransformation of protochlorophyllide (Pchlide) to chlorophyllide (Chlide). chlorophyllide a + NADP(+) = H(+) + NADPH + protochlorophyllide a Porphyrin-containing compound metabolism; chlorophyll biosynthesis. Belongs to the short-chain dehydrogenases/reductases (SDR) family. POR subfamily.