Bacterial expression and site-directed mutagenesis of two critical residues (tyrosine-151 and lysine-155) of human placental NAD+ -dependent 15-hydroxyprostaglandin dehydrogenase
作者:Charles Mark Ensor、Hsin-Hsiung Tai
DOI:10.1016/0167-4838(94)90172-4
日期:1994.9
prostaglandins and NAD+ indicate that the recombinant enzyme does not appear to be kinetically different from the human placental enzyme. Site-directed mutagenesis was used to examine the importance of two residues which are highly conserved in the short-chain dehydrogenases which are known to be related to 15-PGDH. Tyrosine-151 was changed to phenylalanine and serine while lysine-155 was changed to glutamine
NAD(+)依赖的15-羟基前列腺素脱氢酶(15-PGDH)催化前列腺素分解代谢途径的第一步。该酶氧化前列腺素的15-羟基基团,产生通常在生物学上无活性的15-酮代谢产物。在这项研究中,人胎盘15-PGDH的cDNA在大肠杆菌中表达,并将重组酶纯化至均一并进行了表征。对重组蛋白的N末端进行测序,发现与已知的15-PGDH氨基酸序列相同。对许多前列腺素和NAD +的Km和Vmax值的测定表明重组酶似乎与人胎盘酶在动力学上没有差异。使用定点诱变来检查两个残基的重要性,这两个残基在已知与15-PGDH相关的短链脱氢酶中高度保守。酪氨酸151变为苯丙氨酸和丝氨酸,而赖氨酸155变为谷氨酰胺和亮氨酸。Western印迹分析表明突变体和野生型蛋白以相似的水平表达。但是,发现所有的突变蛋白都没有活性。这些结果表明15-PGDH活性需要酪氨酸151和赖氨酸155。发现所有突变蛋白均无活性。这些结果表明15