dehydrogenase/reductase SDR family member 9 (3-alpha hydroxysteroid dehydrogenase, 3alpha-HSD, RDH-E2, short-chain dehydrogenase/reductase retSDR8, NADP-dependent retinol dehydrogenase/reductase, RDHL, DHRS9)

Function

• 3-alpha-hydroxysteroid dehydrogenase
• converts 3-alpha-tetrahydroprogesterone (allopregnanolone) to dihydroxyprogesterone & 3-alpha-androstanediol to dihydroxyprogesterone
• role in the biosynthesis of retinoic acid from retinaldehyde (putative); however, low activity with retinoids
• can utilize both NADH & NADPH

Kinetic parameters:

• KM=9 uM for NADH
• KM=72 uM for NAD
• KM=5 uM for allopregnanolone
• KM=7.5 uM for 3-alpha-androstanediol
• KM=24 uM for androsterone

Structure

• homotetramer
• belongs to the short-chain dehydrogenases/reductases (SDR) family

Compartment

microsomal membrane

Alternative splicing

named isoforms=3

Expression

• expressed in trachea, epidermis > spinal cord, bone marrow, brain, tongue, esophagus, heart, colon, testis, placenta, lung, skeletal muscle, lymph node

More general terms

• dehydrogenase/reductase SDR family (DHRS)
• 3-alpha-hydroxysteroid dehydrogenase
• retinal dehydrogenase

Database

• UniProt: http://www.uniprot.org/uniprot/Q9BPW9.html