大鼠肌肉神经白介素纯化和生化特性及其与磷酸葡萄糖异位酶的关系

通过硫酸铵沉淀、DE_(52)层析、超滤和高压羟基磷灰石层析,从大鼠肌肉条件培养液中得到电泳纯的神经白介素(NLK)。未发现NLK的神经营养活性(维持鸡胚背根神经元存活和促进脊髓神经元突起伸展)及免疫活性(促进外周血单个核细胞产生免疫球蛋白),却有较强的6-磷酸葡萄糖异位酶(GPI)活性。SDS-PAGE测得亚基分子量为56kD;IEF示五条细而相距很近的带,PⅠ值分别为8.20,8.15,8.10,7.90,7.75。Western Blot证实,PAGE和IEF的五条带均可与抗GPI抗体结合,即五种同工酶形式;NLK与GPI的氨基酸组成相近,BrCN水解NLK和GPI得剖相同的肽谱。许多研究表明:NLK不作为一种神经营养因子,而可能是糖酵解酶,即6-磷酸葡萄糖异位酶。

Purification and Characterization of Rat Muscle Neuroleukin and Study on Relationship between Neuroleukin and Glucose Phosphate Isomerase

Neuroleukin (NLK) has been purified from rat muscle conditioned culture medium to homogenity on SDS-PAGE by using combination of ammonium sulfate precipitation, DE_(52) chromatography, YM30 ultrafilter, high pressure hydroxyapatite chromatography. No neurotrophic activities, that supports the survival of cultured sensory neurons and induces axon terminals to sprout,and immune activity, that induces immunoglobulin secretion by cultured human peripheral blood mononuclear cells, were detected as described by M.E. Gurney, yet we have found that each fraction of NLK possessed high 6-glucose phosphate isomerase (GPI)activity. Its subunit molecular weight determined by SDS-PAGE was about 56kD. IEF showed five close-situated thin bands with PI values of 8.20, 8.15, 8.10, 7.90, 7.75, respectively. Western Blot showed that all the five bands in PAGE and IEF were able to combine with antiGPI antibody, which indicated the presence of five isoenzymes. Amino acid composition of NLK was also much like that of GPI from rabbit muscle. The same peptide spectrum hydrolyzed by bromocyanogen was shown between NLK and GPI. Until now, many results suggested that NLK was not a novel neurotrophic, factor but seemed to be a kind of glycolytic enzymes: 6-glucophospate isomerase.