Two different enzymes are primarily responsible for retinoic acid synthesis in rabbit liver cytosol.
Retinoic acid biosynthesis in rabbit liver was catalyzed by cytosolic NAD(+)-dependent dehydrogenase and oxygen-dependent oxidase, with an activity ratio of 59% and 41% in the presence of 2 mM dithiothreitol under aerobic conditions. The two enzymes could be well separated by fractionation involving ammonium sulfate precipitation. Purification of the enzymes indicated that the oxygen-dependent enzyme was a flavoenzyme, retinal oxidase (EC 1.2.3.11), composed of two 135 kDa subunits; and the NAD(+)-dependent enzyme was a basic pI retinal dehydrogenase composed of four 55-kDa subunits. A high concentration (1-2 mM) of DTT was required to stabilize the activity of retinal dehydrogenase during the purification procedures and storage, but inhibited the activity of retinal oxidase by 13-38%. The physiological roles of the two retinoic acid synthases in liver cytosol were discussed.
Huang
D Y
DY
Department of Biochemistry, Kagawa Medical School, Japan.
Ichikawa
Y
Y
D000332:Aerobiosis; D000445:Aldehyde Oxidoreductases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D000693:Anaerobiosis; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003577:Cytochrome P-450 Enzyme System / Q000302:isolation & purification / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D046911:Macromolecular Substances; D008970:Molecular Weight; D010105:Oxygenases / Q000302:isolation & purification / Q000378:metabolism*; D011817:Rabbits; D050697:Retinal Dehydrogenase; D012172:Retinaldehyde / Q000378:metabolism; D013053:Spectrophotometry; D014212:Tretinoin / Q000378:metabolism*
D046911:Macromolecular Substances; D014212:Tretinoin; D003577:Cytochrome P-450 Enzyme System; D010105:Oxygenases; D000445:Aldehyde Oxidoreductases; D050697:Retinal Dehydrogenase; D012172:Retinaldehyde