犬前列腺上皮细胞中5α-还原酶和3α-羟基类固醇脱氢酶的活性

5 Alpha-reductase and 3 alpha-hydroxysteroid dehydrogenase activities in isolated canine prostatic epithelial cells.

作者信息

McKercher G, Chevalier S, Roberts K D, Bleau G, Chapdelaine A

出版信息

J Steroid Biochem. 1984 Nov;21(5):549-54. doi: 10.1016/0022-4731(84)90330-3.

Abstract

Kinetic parameters of two enzymes, 5 alpha-reductase and 3 alpha-hydroxysteroid dehydrogenase, have been calculated for freshly isolated canine prostatic epithelial cells separated into secretory and non-secretory cells on the basis of their density in Percoll gradients. For 5 alpha-reductase, a Km value of 3 X 10(-6) M was obtained in both epithelial cell types, and similar Vmax values of 1.7 X 10(-12) and 1.9 X 10(-12) moles of dihydrotestosterone formed/min/10(6) cells (P greater than 0.50) were calculated in secretory and non-secretory cells, respectively. The Km of 3 alpha-hydroxysteroid dehydrogenase (dihydrotestosterone----3 alpha-androstanediol) varied between 2.2 and 2.8 X 10(-6) M (P greater than 0.50) with respective Vmax's of 9 and 24 X 10(-12) moles of 3 alpha-androstanediol formed/min/10(6) cells (P less than 0.005) in secretory and non-secretory cells. For the reverse reaction, that is the transformation of 3 alpha-androstanediol to dihydrotestosterone, the Km's obtained were 0.4 and 0.5 X 10(-6) M (P greater than 0.50) with Vmax's of 14 and 19 X 10(-12) moles of dihydrotestosterone formed/min/10(6) cells (P less than 0.50) in secretory and non-secretory cells, respectively. Vmax values for 3 alpha-hydroxysteroid dehydrogenase are 10-fold higher than the ones for 5 alpha-reductase. Moreover, Km values for the reaction 3 alpha-androstanediol----DHT are 5-fold lower than those calculated for the reverse reaction and for 5 alpha-reductase. This could explain why the major metabolic pathway in the canine prostate gland is the conversion of 3 alpha-androstanediol to dihydrotestosterone.

摘要

基于在Percoll梯度中细胞的密度，对新鲜分离的犬前列腺上皮细胞（分为分泌细胞和非分泌细胞）的两种酶——5α-还原酶和3α-羟基类固醇脱氢酶的动力学参数进行了计算。对于5α-还原酶，在两种上皮细胞类型中均获得了3×10⁻⁶ M的Km值，在分泌细胞和非分泌细胞中分别计算出相似的Vmax值，即每分钟每10⁶个细胞形成1.7×10⁻¹²和1.9×10⁻¹²摩尔二氢睾酮（P＞0.50）。3α-羟基类固醇脱氢酶（二氢睾酮→3α-雄甾二醇）的Km在2.2至2.8×10⁻⁶ M之间变化（P＞0.50），在分泌细胞和非分泌细胞中，相应的Vmax分别为每分钟每10⁶个细胞形成9和24×10⁻¹²摩尔3α-雄甾二醇（P＜0.005）。对于逆反应，即3α-雄甾二醇转化为二氢睾酮，获得的Km值分别为0.4和0.5×10⁻⁶ M（P＞0.50），在分泌细胞和非分泌细胞中，Vmax分别为每分钟每10⁶个细胞形成14和19×10⁻¹²摩尔二氢睾酮（P＜0.50）。3α-羟基类固醇脱氢酶的Vmax值比5α-还原酶的Vmax值高10倍。此外，3α-雄甾二醇→双氢睾酮反应的Km值比逆反应和5α-还原酶计算出的Km值低5倍。这可以解释为什么犬前列腺中的主要代谢途径是3α-雄甾二醇转化为二氢睾酮。