【摘要】 研究了冬枣果实苯丙氨酸解氨酶(PAL)的酶学特性。L-苯丙氨酸为枣果实PAL的反应底物,结果表明,最适底物浓度为1.0 mmol/L。枣果实PAL属于别构酶,具有2个米氏常数,Km分别为0.115×10-4、8.177×10-4 mol/L。枣果实PAL最适温度为50℃,最适p H为8.8。在浓度为0~4.0 mmol/L范围里,L-半胱氨酸、酪氨酸、色氨酸、组氨酸均对枣果实PAL活性有一定的抑制作用,而抗坏血酸和蔗糖对PAL有激活作用。金属离子对PAL激活作用由强到弱依次为:Cu2+>Fe3+>Fe2+>Na+;金属离子对PAL抑制作用由强到弱依次为:Al3+>Mg2+>Mn2+>Ca2+>Zn2+>K+。研究结果揭示了冬枣果实PAL酶学特性,为通过调控枣果实PAL酶活性改善果实贮藏特性提供了理论依据。更多还原

【Abstract】 The characteristics of phenylalanine ammonia-lyase(PAL) in jujube fruit were studied. Results showed that the optimum concentration of the reaction substrate(L-phenylalanine) was identified to 1.0 mmol/L. PAL in jujube fruit was evidenced as a kind of allosteric enzyme that possesses two Michaelis constant. Values of Km were 0.115×10-4 mol/L and 8.177×10-4 mol/L. The optimum temperature for reaction of the enzyme was identified to 50 ℃, and the optimum p H was 8.8. In the concentration range from 0 mmol/L to 4.0 mmol/L, PAL activity was inhibited by the following agents: L-cysteine, tyrosine, tryptophan, and histidine, but was stimulated by ascorbic acid and sucrose. Some metal ions could activate the PAL activity, including(from strong to weak): Cu2+>Fe3+>Fe2+>Na+. Whereas, other metal ions that could inhibit the PAL activity were as the followings: Al3+>Mg2+>Mn2+>Ca2+>Zn2+>K+. The results revealed the characteristics of PAL in Dongzao jujube fruit and provided theoretical basis for improving fruit storage quality via the regulation of PAL activity of the jujube fruit.更多还原