Probable iron-sulfur flavoprotein that converts 7-hydroxymethyl chlorophyll a to chlorophyll a using ferredoxin as a reducing equivalent. Catalyzes the reduction of a hydroxymethyl group to a methyl group. Belongs to the chlorophyll catabolic enzymes (CCEs). chlorophyll a + H2O + 2 oxidized [2Fe-2S]-[ferredoxin] = 7(1)-hydroxychlorophyll a + 2 H(+) + 2 reduced [2Fe-2S]-[ferredoxin] Interacts with SGR1, the chlorophyll catabolic enzymes (CCEs) NYC1, NOL and RCCR, and the LHCII complex. Part of a SGR1-CCE-LHCII complex, which acts in chlorophyll breakdown. Constantly expressed throughout development. No visible phenotype under normal growth conditions, but plants accumulate 7-hydroxymethyl chlorophyll a in green leaves. Belongs to the FrhB family.