Human liver 6-pyruvoyl tetrahydropterin reductase is biochemically and immunologically indistinguishable from aldose reductase.

6-Pyruvoyl tetrahydropterin reductase has been implicated in the biosynthesis of tetrahydrobiopterin. Using immunochemical and biochemical techniques the purified human liver enzyme was shown to be identical to aldose reductase. This suggests that 6-pyruvoyl tetrahydropterin reductase may play an additional role in the reduction of aldehydes derived from the biogenic amine neuro-transmitters and corticosteroid hormones as well as in the pathogenesis of diabetic complications, as has been postulated for aldose reductase.