Chlorophyll(ide) b reductase

Chlorophyll(ide) b reductase (EC 1.1.1.294, chlorophyll b reductase, Chl b reductase) is an enzyme with systematic name 71-hydroxychlorophyllide-a:NAD(P)⁺ oxidoreductase. This enzyme catalyses the following chemical reaction

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.