Fincham N, Camp R
Biochem J. 1983 Apr 15;212(1):129-34. doi: 10.1042/bj2120129.
Present evidence suggests that skin is an important organ of prostaglandin metabolism. To clarify its role, the basic kinetics of 15-hydroxyprostaglandin dehydrogenase (PGDH) from rat skin were investigated with either NAD+ of NADP+ as co-substrate. Prostaglandin F2 alpha (PGF2 alpha) and prostaglandin E2 (PGE2) were used as substrates and preliminary studies were made of the inhibitory effects of the reduced co-substrates NADH and NADPH. A radiochemical assay was used in which [3H]PGF2 alpha or [14C]PGE2 were incubated with high-speed supernatant of rat skin homogenates. The substrate and products were then extracted by solvent partition, separated by t.l.c. and quantified by liquid-scintillation counting. At linear reaction rates and at an NAD+ concentration of 10 mM the mean apparent Km for PGF2 alpha was 24 microM with a mean apparent Vmax. of 9.8 nmol/s per litre of reaction mixture. For PGE2 the mean apparent Km was 8 microM, with a mean apparent Vmax, of 2.7 nmol/s per litre of reaction mixture. With NADP+ as a co-substrate at a concentration of 5 mM a mean apparent Km of 23 microM was obtained for PGF2 alpha with a mean apparent Vmax. of 5.2 nmol/s per litre. For PGE2 values of 7.5 microM and 3.0 nmol/s per litre were obtained respectively. These results show that skin contains NAD+- and NADP+-dependent PGDH. An important finding was that the NADP+-linked enzyme gave Km values for PGE2 that were considerably lower than those reported for NADP+-linked PGDH from other tissues. Furthermore, preliminary inhibition studies with the NAD+-linked PGDH system indicate that this enzyme is not only inhibited by NADH, but also by NADPH, a property not previously reported for NAD+-linked PGDH derived from other tissues.
现有证据表明，皮肤是前列腺素代谢的重要器官。为阐明其作用，以NAD⁺或NADP⁺作为共底物，研究了大鼠皮肤中15 - 羟基前列腺素脱氢酶（PGDH）的基本动力学。以前列腺素F2α（PGF2α）和前列腺素E2（PGE2）作为底物，并对还原型共底物NADH和NADPH的抑制作用进行了初步研究。采用放射化学分析法，将[³H]PGF2α或[¹⁴C]PGE2与大鼠皮肤匀浆的高速上清液一起孵育。然后通过溶剂分配提取底物和产物，用薄层层析法分离，并用液体闪烁计数法定量。在线性反应速率下，当NAD⁺浓度为10 mM时，PGF2α的平均表观Km为24 μM，平均表观Vmax为每升反应混合物9.8 nmol/s。对于PGE2，平均表观Km为8 μM，平均表观Vmax为每升反应混合物2.7 nmol/s。以NADP⁺作为浓度为5 mM的共底物时，PGF2α的平均表观Km为23 μM，平均表观Vmax为每升5.2 nmol/s。对于PGE2，分别得到7.5 μM和每升3.0 nmol/s的值。这些结果表明，皮肤含有依赖NAD⁺和NADP⁺的PGDH。一个重要发现是，与NADP⁺相关的酶对PGE2的Km值明显低于其他组织中报道的与NADP⁺相关的PGDH的Km值。此外，对与NAD⁺相关的PGDH系统的初步抑制研究表明，该酶不仅受到NADH的抑制，还受到NADPH的抑制，这是其他组织来源的与NAD⁺相关的PGDH以前未报道过的特性。
