Panel A, Reduction of Cygb1 by zebrafish CYB5a and CYB5R. Panel B, Reduction of Cygb2 by zebrafish CYB5a and CYB5R. Panel C, Reduction of GlobinX by zebrafish CYB5a and CYB5R, Panel D, Reduction of Cygb1 by zebrafish CYB5b and CYB5R (solid lines) or the human CYB5b/CYB5R system (dotted lines). Panel E, Reduction of Cygb2 by zebrafish CYB5b and CYB5R (solid lines) or the human CYB5b/CYB5R system (dotted lines). Panel F, Reduction of GlobinX by zebrafish CYB5b and CYB5R (solid lines) or the human CYB5b/CYB5R system (dotted lines). Red lines, reactions monitored at 25 °C, Black lines, reactions monitored at 37 °C.