Satoh Motonobu, Iwahori Tsuguya, Sugawara Naoki, Yamazaki Masatoshi
Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, Teikyo University, Sagamiko, Kanagawa, Japan.
J Endotoxin Res. 2006;12(1):21-38. doi: 10.1179/096805106X89062.
The liver is known to clear and detoxify circulating lipopolysaccharide (LPS). To characterize the molecules involved in this process in the liver, we attempted to purify mouse liver protein(s) that can interact with lipid A, a biologically active portion of LPS. By partially purifying the inactivating activity against a synthetic lipid A analog, we observed the enrichment of a 45-kDa protein in the active fractions. The internal amino acid sequences of the protein were identical with those of argininosuccinate synthase (EC 6.3.4.5). To examine whether argininosuccinate synthase can interact with lipid A, we purified the enzyme from mouse liver and found the co-elevation of the specific enzyme activity and specific lipid A-inactivating activity, indicating that argininosuccinate synthase is the major lipid A-interacting protein in liver. Argininosuccinate synthase also inhibited the biological activities (macrophage activation and Limulus test) of natural lipid A and rough-type LPS but not smooth-type LPS. The enzyme activity was inhibited by lipid A and rough-type LPS and also by smooth-type LPS. Native gel electrophoresis of a mixture of argininosuccinate synthase and LPS and immunoprecipitation of a mixture of argininosuccinate synthase and [(3)H]-LPS with anti-argininosuccinate synthase antiserum showed that argininosuccinate synthase stably bound lipid A and LPS. These findings, together, indicate that argininosuccinate synthase can effectively bind LPS in the liver.
已知肝脏可清除循环中的脂多糖（LPS）并使其解毒。为了鉴定肝脏中参与此过程的分子，我们试图纯化能够与LPS的生物活性部分脂质A相互作用的小鼠肝脏蛋白。通过部分纯化针对合成脂质A类似物的失活活性，我们观察到活性级分中一种45 kDa蛋白的富集。该蛋白的内部氨基酸序列与精氨琥珀酸合酶（EC 6.3.4.5）的序列相同。为了检测精氨琥珀酸合酶是否能与脂质A相互作用，我们从小鼠肝脏中纯化了该酶，发现酶的比活性和脂质A特异性失活活性共同升高，这表明精氨琥珀酸合酶是肝脏中主要的脂质A相互作用蛋白。精氨琥珀酸合酶还抑制天然脂质A和粗糙型LPS的生物活性（巨噬细胞活化和鲎试剂检测），但不抑制光滑型LPS的生物活性。脂质A、粗糙型LPS以及光滑型LPS均可抑制该酶的活性。精氨琥珀酸合酶与LPS混合物的非变性凝胶电泳以及精氨琥珀酸合酶与[³H]-LPS混合物用抗精氨琥珀酸合酶抗血清进行的免疫沉淀表明，精氨琥珀酸合酶能稳定结合脂质A和LPS。这些发现共同表明，精氨琥珀酸合酶能够在肝脏中有效结合LPS。
