71-hydroxychlorophyllide a + NAD(P)+ chlorophyllide b + NAD(P)H + H+
This enzyme carries out the first step in the conversion of chlorophyll b to chlorophyll a. It is involved in chlorophyll degradation, which occurs during leaf senescence, and it also forms part of the chlorophyll cycle, which interconverts chlorophyll a and b in response to changing light conditions.
^Rüdiger W (2002). "Biosynthesis of chlorophyll b and the chlorophyll cycle". Photosynthesis Research. 74 (2): 187–93. doi:10.1023/A:1020959610952. PMID16228557.