Omichi K, Ikenaka T
J Biochem. 1986 Apr;99(4):1245-52. doi: 10.1093/oxfordjournals.jbchem.a135588.
The modes of action of four alpha-amylase isozymes, which were purified from human saliva, on p-nitrophenyl alpha-maltopentaoside (G5P), maltohexaitol (G6R), and their 2-pyridylamino derivatives, p-nitrophenyl O-6-deoxy-6-[(2-pyridyl)amino]-alpha-D-glucopyranosyl-(1----4)-O-alpha- D-glucopyranosyl-(1----4)-O-alpha-D-glucopyranosyl-(1----4)-O-alpha-D- glucopyranosyl-(1----4)-alpha-D-glucopyranoside (FG5P) and O-6-deoxy-6-[(2-pyridyl)amino]-alpha-D-glucopyranosyl-(1----4)- O-alpha-D-glucopyranosyl-(1----4)-O-alpha-D-glucopyranosyl-(1----4)-O- alpha-D-glucopyranosyl-(1----4)-O-alpha-D-glucopyranosyl-(1----4)-D- glucitol (FG6R) were examined at various pH values. No differences in their modes of action on the substrates was found. Irrespective of which enzyme was used, the molar ratio of the hydrolysis products of G5P or G6R was almost constant at any pH examined. On the other hand, those of FG5P and FG6R varied with pH such that predominantly O-6-deoxy-6-[(2-pyridyl)amino]-alpha-D-glucopyranosyl- (1----4)-O-alpha-D-glucopyranosyl-(1----4)-D-glucose (FG3) was formed at high pH ranges, while the formation of O-6-deoxy-6-[(2-pyridyl)amino]-alpha-D-glucopyranosyl-(1----4)- O-alpha-D-glucopyranosyl-(1----4)-O-alpha-D-glucopyranosyl-(1----4)-D-gl ucose (FG4) increased at lower pH. The result indicates that the binding mode of FG5P or FG6R to the active sites of the enzymes changed with pH; namely, interactions between the 2-pyridylamino residue of the substrates and some amino acid residue(s) located in the active sites were influenced by pH.(ABSTRACT TRUNCATED AT 250 WORDS)
对从人唾液中纯化得到的四种α-淀粉酶同工酶作用于对硝基苯基α-麦芽五糖苷（G5P）、麦芽六糖醇（G6R）及其2-吡啶基氨基衍生物、对硝基苯基O-6-脱氧-6-[(2-吡啶基)氨基]-α-D-吡喃葡萄糖基-(1→4)-O-α-D-吡喃葡萄糖基-(1→4)-O-α-D-吡喃葡萄糖基-(1→4)-O-α-D-吡喃葡萄糖基-(1→4)-α-D-吡喃葡萄糖苷（FG5P）和O-6-脱氧-6-[(2-吡啶基)氨基]-α-D-吡喃葡萄糖基-(1→4)-O-α-D-吡喃葡萄糖基-(1→4)-O-α-D-吡喃葡萄糖基-(1→4)-O-α-D-吡喃葡萄糖基-(1→4)-O-α-D-吡喃葡萄糖基-(1→4)-D-葡萄糖醇（FG6R）的作用模式在不同pH值下进行了研究。未发现它们对底物的作用模式存在差异。无论使用哪种酶，在任何检测的pH值下，G5P或G6R水解产物的摩尔比几乎恒定。另一方面，FG5P和FG6R的水解产物摩尔比随pH值变化，使得在高pH范围内主要形成O-6-脱氧-6-[(2-吡啶基)氨基]-α-D-吡喃葡萄糖基-(1→4)-O-α-D-吡喃葡萄糖基-(1→4)-D-葡萄糖（FG3），而在较低pH值下O-6-脱氧-6-[(2-吡啶基)氨基]-α-D-吡喃葡萄糖基-(1→4)-O-α-D-吡喃葡萄糖基-(1→4)-O-α-D-吡喃葡萄糖基-(1→4)-D-葡萄糖（FG4）的形成增加。结果表明，FG5P或FG6R与酶活性位点的结合模式随pH值变化；即底物的2-吡啶基氨基残基与位于活性位点的某些氨基酸残基之间的相互作用受pH值影响。（摘要截于250字）
