Shih T W, Shealy Y F, Hill D L
Southern Research Institute, Kettering Meyer Laboratory, Birmingham, AL 35255-5305.
Drug Metab Dispos. 1988 May-Jun;16(3):337-40.
Enzymatic activity present in liver microsomes from rats slowly hydrolyzed N-(4-hydroxyphenyl)retinamide (4HPR). A product of the reaction was all-trans-retinoic acid. The reaction, which had a pH optimum greater than 8.6, was stimulated by divalent cations, particularly Mn2+. Enzyme activity was highest in liver microsomes but was also present in kidney microsomes, liver cytoplasm, and spleen cytoplasm. Of 10 possible substrates tested, the 13-cis- and all-trans-forms of N-ethylretinamide were most active. The all-trans-form of 4HPR was much more active than the 13-cis-form. Neither 13-cis- nor all-trans-retinoyl leucine was a substrate. Because no detectable [14C]all-trans-retinoic acid could be found in the livers of rats after doses of [14C]4HPR, we conclude that this enzyme is not extensively active in intact animals.
大鼠肝脏微粒体中的酶活性可缓慢水解N-(4-羟基苯基)视黄酰胺(4HPR)。反应产物为全反式维甲酸。该反应的最适pH大于8.6，受二价阳离子尤其是Mn2+的刺激。酶活性在肝脏微粒体中最高，但在肾脏微粒体、肝脏细胞质和脾脏细胞质中也有存在。在所测试的10种可能底物中，N-乙基视黄酰胺的13-顺式和全反式形式活性最高。4HPR的全反式形式比13-顺式形式活性高得多。13-顺式和全反式视黄酰亮氨酸均不是底物。由于给大鼠注射[14C]4HPR后，在其肝脏中未发现可检测到的[14C]全反式维甲酸，我们得出结论，该酶在完整动物体内活性不高。
