... cofactor, and has a much greater catalytic efficiency as a reductase than as a dehydrogenase The catalytic efficiency of RDH13 as a retinaldehyde reductase is significantly lower than that of a related protein ... enzymatic activity was observed after several months of storage HPLC analysis of RDH13 activity The catalytic activity of RDH13–His6 and the RDH13-containing mitochondrial fraction was assayed as ... and cofactors [21], because the outer mitochondrial membrane is highly permeable This is consistent with the function of RDH13 as a retinaldehyde reductase, as both retinaldehyde and NADPH can...