Shih T W, Hill D L
Southern Research Institute, Birmingham, AL 35255-5305.
Drug Metab Dispos. 1991 Mar-Apr;19(2):332-5.
An NADPH-requiring enzyme present in rat liver microsomes catalyzes the conversion of retinol to retinal; the enzyme activity is induced by 3-methylcholanthrene (MC). The optimum activities for both the constitutive and induced reactions occur within a pH range of 8.2-8.7. For the constitutive enzyme, the KM and Vmax values are 285 microM retinol and 18 nmol of retinal/mg protein/hr, respectively; for the MC-induced activity, the corresponding values are 133 microM retinol and 33 nmol of retinal/mg protein/hr. Neither the constitutive nor the induced activities are detectable in microsomes from seven other tissues. Both hepatic activities are inhibited by citral, ketoconazole, SKF 525-A, and alpha-naphthoflavone; both are stimulated by divalent cations. Neither is inhibited by 3-amino-1,2,4-triazole, pyrazole, or sodium azide or stimulated by monovalent cations. The enzyme appears to be a previously unreported retinol oxidase, distinct from the known cytosolic enzymes, retinal reductase and retinol dehydrogenase.
大鼠肝脏微粒体中存在的一种需要NADPH的酶催化视黄醇转化为视黄醛；该酶活性可被3-甲基胆蒽（MC）诱导。组成型反应和诱导型反应的最佳活性均出现在pH 8.2 - 8.7范围内。对于组成型酶，KM和Vmax值分别为285μM视黄醇和18 nmol视黄醛/毫克蛋白/小时；对于MC诱导的活性，相应的值分别为133μM视黄醇和33 nmol视黄醛/毫克蛋白/小时。在其他七种组织的微粒体中均未检测到组成型或诱导型活性。两种肝脏活性均受到柠檬醛、酮康唑、SKF 525 - A和α-萘黄酮的抑制；两者均受到二价阳离子的刺激。两者均不受3 - 氨基 - 1,2,4 - 三唑、吡唑或叠氮化钠的抑制，也不受一价阳离子的刺激。该酶似乎是一种以前未报道过的视黄醇氧化酶，与已知的胞质酶视黄醛还原酶和视黄醇脱氢酶不同。
