Laboratory of Biochemistry, Gifu Pharmaceutical University, Gifu 501-1196, Japan.
Forensic Science Laboratory, Gifu Prefectural Police Headquarters, Gifu 500-8501, Japan.
J Steroid Biochem Mol Biol. 2022 Jul;221:106113. doi: 10.1016/j.jsbmb.2022.106113. Epub 2022 Apr 6.
Most members of the aldo-keto reductase (AKR) 1 C subfamily are hydroxysteroid dehydrogenases (HSDs). Similarly to humans, four genes for AKR1C proteins (AKR1C1-AKR1C4) have been identified in the pig, which is a suitable species for biomedical research model of human diseases and optimal organ donor for xenotransplantation. Previous study suggested that, among the porcine AKR1Cs, AKR1C1 and AKR1C4 play important roles in steroid hormone metabolism in the reproductive tissues; however, their biological functions are still unknown. Herein, we report the biochemical properties of the two recombinant enzymes. Kinetic and product analyses of steroid specificity indicated that AKR1C1 is a multi-specific reductase, which acts as 3α-HSD for 3-keto-5β-dihydro-C/C-steroids, 3β-HSD for 3-keto-5α-dihydro-C-steroids including androstenone, 17β-HSD for 17-keto-C-steroids including estrone, and 20α-HSD for progesterone, showing K values of 0.5-11 µM. By contrast, AKR1C4 exhibited only 3α-HSD activity for 3-keto groups of 5α/β-dihydro-C-steroids, 5β-dihydro-C-steroids and bile acids (K: 1.0-1.9 µM). AKR1C1 and AKR1C4 also showed broad substrate specificity for nonsteroidal carbonyl compounds including endogenous 4-oxo-2-nonenal, 4-hydroxy-nonenal, acrolein, isocaproaldehyde, farnesal, isatin and methylglyoxal, of which 4-oxo-2-nonenal was reduced with the lowest K value of 0.9 µM. Moreover, AKR1C1 had the characteristic of reducing aliphatic ketones and all-trans-retinal. The enzymes were inhibited by flavonoids, synthetic estrogens, nonsteroidal anti-inflammatory drugs, triterpenoids and phenolphthalein, whereas only AKR1C4 was activated by bromosulfophthalein. These results suggest that AKR1C1 and AKR1C4 function as 3α/3β/17β/20α-HSD and 3α-HSD, respectively, in metabolism of steroid hormones and a sex pheromone androstenone, both of which also play roles in metabolism of nonsteroidal carbonyl compounds.
大多数醛酮还原酶（AKR）1C 亚家族成员都是羟甾体脱氢酶（HSD）。与人类相似，猪中已鉴定出 4 种 AKR1C 蛋白（AKR1C1-AKR1C4）基因，猪是研究人类疾病的生物医学模型和异种移植的最佳器官供体的合适物种。先前的研究表明，在猪 AKR1C 中，AKR1C1 和 AKR1C4 在生殖组织中的类固醇激素代谢中发挥重要作用；然而，它们的生物学功能仍不清楚。在此，我们报告了这两种重组酶的生化特性。类固醇特异性的动力学和产物分析表明，AKR1C1 是一种多特异性还原酶，它是 3-酮-5β-二氢-C/C-甾体的 3α-HSD、3-酮-5α-二氢-C-甾体（包括雄烯酮）的 3β-HSD、17-酮-C-甾体（包括雌酮）的 17β-HSD 和孕激素的 20α-HSD，其 K 值为 0.5-11µM。相比之下，AKR1C4 仅对 5α/β-二氢-C-甾体、5β-二氢-C-甾体和胆汁酸的 3-酮基团表现出 3α-HSD 活性（K：1.0-1.9µM）。AKR1C1 和 AKR1C4 对包括内源性 4-氧代-2-壬烯醛、4-羟基壬烯醛、丙烯醛、异己醛、法呢醛、色氨酸和甲基乙二醛在内的非甾体羰基化合物也表现出广泛的底物特异性，其中 4-氧代-2-壬烯醛的 K 值最低，为 0.9µM。此外，AKR1C1 具有还原脂肪族酮和全反式视黄醛的特征。这些酶被黄酮类、合成雌激素、非甾体抗炎药、三萜类和酚酞抑制，而只有 AKR1C4 被溴磺酞激活。这些结果表明，AKR1C1 和 AKR1C4 分别作为 3α/3β/17β/20α-HSD 和 3α-HSD 参与类固醇激素和性信息素雄烯酮的代谢，两者还参与非甾体羰基化合物的代谢。
