1.3.7.3	(3Z)-phycoerythrobilin + oxidized ferredoxin = 15,16-dihydrobiliverdin + reduced ferredoxin + 2 H+	-	-	
1.3.7.3	(3Z)-phycoerythrobilin + oxidized ferredoxin = 15,16-dihydrobiliverdin + reduced ferredoxin + 2 H+	analysis of the reaction mechanism, after binding of 15,16-dihydrobiliverdin (DHBV) to the enzyme, Asp99 delivers a proton to the A-ring oxygen, forming a positively charged DHBVH+. After acceptance of an electron from ferredoxin, the A-ring pyrrole proton tautomerizes to the C2 position and is stabilized there. This is facilitated by the catalytic action of the axial water, which is activated/positioned by Asp219 and (indirectly) by Arg215. For the second protonation step, the reprotonation of the A-ring nitrogen, uptake of another electron, and a final tautomerization to yield the product PEB is assumed, flipped binding mode for PEB biosynthesis	-, 763264