Mega T, Nakamura N, Ikenaka T
Department of Chemistry, Osaka University College of Science.
J Biochem. 1990 Jan;107(1):68-72. doi: 10.1093/oxfordjournals.jbchem.a123013.
The beta-elimination and nucleophile addition reactions of the substituted serine and threonine residues were studied using several synthesized fluorescence-labeled phosphopeptides and a salmon egg polysialoglycoprotein (PSGP). The reagents used were 1 M CH3SH-0.43 M NaOH, 1 M NaBH4-0.1 M NaOH, 1 M CH3NH2-0.1 M NaOH, and 1 M Na2SO3-0.1 M NaOH. The beta-elimination reaction of a phosphoserine peptide, Gly-Ser(PO4)-Glu-AEAP, was about 20 times faster than that of the corresponding phosphothreonine peptide. The carboxyl-side amino acid of the phosphoamino acids in peptides greatly affected the beta-elimination rate. The beta-elimination reaction rates of O-glycosyl serine and threonine in the polysialoglycoprotein were similar and were about a half of that of the phosphoserine peptide. The rates of addition of the three nucleophiles and hydrogen to alpha-aminoacrylic acid (beta-elimination product of substituted serine) in the peptide decreased in the order of CH3SH, Na2SO3, CH3NH2, and H2(NaBH4), and the addition to alpha-aminocrotonic acid (beta-elimination product of substituted threonine) in the order of Na2SO3, CH3NH2, CH3SH, and H2. These results indicated that sulfite is the most recommended nucleophile because of its high addition rate. If sulfite addition is carried out in the presence of NaBH4, sugar chains can be released as alditols, converting the sugar-attaching amino acids to beta-sulfoamino acids.
使用几种合成的荧光标记磷酸肽和鲑鱼卵多唾液酸糖蛋白（PSGP）研究了取代丝氨酸和苏氨酸残基的β-消除反应和亲核加成反应。所使用的试剂为1 M CH3SH - 0.43 M NaOH、1 M NaBH4 - 0.1 M NaOH、1 M CH3NH2 - 0.1 M NaOH和1 M Na2SO3 - 0.1 M NaOH。磷酸丝氨酸肽Gly-Ser(PO4)-Glu-AEAP的β-消除反应速度比相应的磷酸苏氨酸肽快约20倍。肽中磷酸氨基酸的羧基侧氨基酸对β-消除速率有很大影响。多唾液酸糖蛋白中O-糖基化丝氨酸和苏氨酸的β-消除反应速率相似，约为磷酸丝氨酸肽的一半。肽中三种亲核试剂和氢对α-氨基丙烯酸（取代丝氨酸的β-消除产物）的加成速率按CH3SH、Na2SO3、CH3NH2和H2(NaBH4)的顺序降低，对α-氨基巴豆酸（取代苏氨酸的β-消除产物）的加成速率按Na2SO3、CH3NH2、CH3SH和H2的顺序降低。这些结果表明，亚硫酸盐因其高加成速率而成为最推荐的亲核试剂。如果在NaBH4存在下进行亚硫酸盐加成，糖链可以以糖醇形式释放，将连接糖的氨基酸转化为β-磺基氨基酸。
