The AKR1B family of AKR includes aldose reductase (AR, EC 1.1.1.21) from Homo sapiens (AKR1B1), Oryctolagus cuniculus (kidney, AKR1B2), Mus musculus (AKR1B3), Rattus norvegicus (lens, AKR1B4), Bos taurus (lens/testis, AKR1B5), and Sus scrofa (lens, AKR1B6), aldose reductase-related protein 1 (ALD1, EC1.1.1.21) from Mus musculus (AKR1B7), Rattus norvegicus (AKR1B14), and Homo sapiens (AKR1B15), Mus musculus fibroblast growth factor induced protein (FR-1 or AKR1B8, EC 1.1.1.21), Cricetulus griseus aldose reductase-related protein 2 (ALD2 or AKR1B9, EC 1.1.1.21), aldose reductase-like from Homo sapiens (ARL-1 or AKR1B10) and Rattus norvegicus (AKR1B13), aldo-keto reductase from Gallus domesticus (eye, tongue, esophagus, AKR1B12), and Oryctolagus cuniculus AR-like protein (3beta-HSD, AKR1B19). AR, also called aldehyde reductase, catalyzes the NADPH-dependent reduction of a wide variety of carbonyl-containing compounds to their corresponding alcohols with a broad range of catalytic efficiencies. ALD1 reduces a broad range of aliphatic and aromatic aldehydes to the corresponding alcohols. It may play a role in the metabolism of xenobiotic aromatic aldehydes. FR-1, also called aldose reductase-related protein 2, or fibroblast growth factor-regulated protein (FGFRP), is induced by fibroblast growth factor-1. It may play a role in the regulation of the cell cycle. FR-1 belongs to the NADPH-dependent aldo-keto reductase family. ALD2 is an inducible aldo-keto reductase with a preference for aliphatic substrates. It can also act on small aromatic aldehydes, steroid aldehydes and some ketone substrates. ARL-1, also called aldose reductase-like, or aldose reductase-related protein (ARP), or small intestine reductase, or SI reductase, acts as all-trans-retinaldehyde reductase that can efficiently reduce aliphatic and aromatic aldehydes, and is less active on hexoses (in vitro). It may be responsible for detoxification of reactive aldehydes in the digested food before the nutrients are passed on to other organs. AKR1B15, also called estradiol 17-beta-dehydrogenase AKR1B15, is a mitochondrial aldo-keto reductase that catalyzes the reduction of androgens and estrogens with high positional selectivity (shows 17-beta-hydroxysteroid dehydrogenase activity) as well as 3-keto-acyl-CoAs. It has a strong selectivity towards NADP(H). AKR1B19 is aldose reductase-like that may show 3-beta-hydroxysteroid dehydrogenase (3beta-HSD) activity.
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