Purification and some properties of an amine oxidase from soybean seedlings

Summary An amine oxidase was purified 447-fold from soybean seedlings and some of its properties were investigated. The molecular weight of the enzyme was estimated to be 25,000. It was most active towards putrescine, followed by spermidine and spermine. K_m-values for these substrates were relatively close. The enzyme was strongly inhibited by carbonyl reagents, such as semicarbazide and aminoguanidine.     

Administration of D-alanine did not cause increase of D-amino acid oxidase activity in mice

D-amino acid oxidase (DAAO) activity was not altered in the liver and kidney by oral administration of D-alanine to adult mice. The enzyme was apparently not induced by the enteric microflora either, since the enzyme activity in the liver and kidney of germ-free mice was not different from that of specific-pathogen-free mice. The times of appearance of DAAO activity and of free D-amino acids in the kidney were elucidated using suckling mice. DAAO activity started to increase 7 days after birth, and reached almost the adult level by 28 days. The content of free neutral D-amino acids also increased with age, in a similar fashion. A possible conclusion is that the enzyme activity normally increases during this period, to eliminate the free D-amino acids which have increased with age in the suckling mice. Consequently, the administration of D-alanine had no further effect in increasing enzyme activity.     

Biosynthesis of ascorbic acid in chick embryos

Summary Biosynthesis of ascorbic acid was found in the kidneys (mesonephros and metanephros) of the chick embryo as well as in the yolk sac membrane. The activity of L-gulonolactone oxidase in the yolk sac membrane suggested that it was the major source of ascorbic acid in the chick embryo.I am grateful to Dr R. Jenness (Univ. of Minnesota) for the generous gift of L-gulonolactone and to Dr B. Sanders (Univ. of Texas) for the chick embryo samples     

莲藕中多酚氧化酶的性质

以冷冻丙酮制备莲藕多酚氧化酶丙酮粉，用分光光度法研究pH值、温度、底物浓度、抑制剂对酶活性的影响.结果表明，以邻苯二酚为底物，莲藕ppo的最适pH值为7.0，最适温度为35 ℃；Km为22.7 mmol/L，Vm为0.625 OD/min，100 ℃热处理25 s可钝化ppo的活性；抗坏血酸、亚硫酸钠为强烈抑制剂，1.75×10^-4的抗坏血酸和3.00×10^-4 的亚硫酸钠能有效抑制ppo的活性.     

山茶属七种植物部分生理生化特性的比较研究

对山茶属７种野生植物的多酚氧化酶同工酶、茶多酚含量和超氧化歧化酶活力进行测试分析，结果显示它们的ＰＬ活力，ＴＰ含量和ＳＯＤ活力的种间变异系数分别达３４．８７，８９．２２％和２４．９６：多酚氧化酶同工酶谱带型相似，ＰＬ生理活力强弱随其原生生态环境相似而聚类。     

TS制剂对桑树萎缩病的防治机理

用植物病毒防治剂（ＴｈｅＶｉｒｏｃｉｄｅｆｏｒＰｌａｎｔ）—ＴＳ制剂喷洒感病桑树植株后,用聚丙烯酰胺凝胶电泳对叶片多酚氧化酶、过氧化物酶进行同功酶比较,发现处理株多酚氧化酶的酶带数和对照株相同,均为４条,但酶带位置、强弱有差异;处理株过氧化物酶有４条基本酶带,而对照株有３条酶带,处理株出现一条新酶带．处理株多酚氧化酶活性感病后期比感病初期提高１．６倍,对照株酶活性提高１倍,而过氧化物酶活性感病后期比感病初期下降６０％,而对照株酶活性下降８０％．用紫外分光光度计测蛋白质含量,处理组为０．３ｇ／Ｌ,对照组为０．３８ｇ／Ｌ,表明经ＴＳ制剂处理比对照桑萎缩病的病株蛋白质含量降低．     

酶形式差异的三酶系统一步法转化头孢菌素C制备7-氨基头孢烷酸

【目的】对酶形式差异的三酶系统一步法裂解头孢菌素C(CPC)制备7-氨基头孢烷酸(7-ACA)进行研究。【方法】对重组大肠杆菌分别进行摇瓶和发酵罐高密度表达,获得最高酶活后使用两个形式差异的三酶系统一步法转化CPC制备7-ACA。【结果】相较于摇瓶发酵,发酵罐发酵获得的酶活更高,发酵罐上对重组大肠杆菌的高密度表达发现,补料流加总量为400mL的甘油混合液(15%甘油+7.5%鱼蛋白胨,W/V),发酵72h后菌浓度达到32.79g/L、最高的戊二酰-7-氨基头孢烷酸酰化酶(GA)和过氧化氢酶(CAT)活力分别为7 099.85U/L和15 776.20U/L。利用一个三酶系统包括固定化D-氨基酸氧化酶(DAAO)、游离GA和CAT,一步法催化CPC获得的7-ACA生成率为87.28%;而另一个三酶系统包括固定化DAAO、冻融细胞GA和CAT一步法催化CPC获得的7-ACA生成率为87.10%。【结论】两种酶形式差异的三酶系统一步法制备7-ACA的得率大致相等。GA对α?酮己二酰-7-氨基头孢烷酸(AKA-7-ACA)的特异性和水解能力较差,限制了该工艺运用。     

磁场影响GOD催化活性的初步探讨

本文成功地研制了ＰＶＣ葡萄糖氧化酶（ＧＯＤ）柱，用流动装置和Ｉ电极探讨了磁场对ＧＯＤ活性的影响：密闭条件下磁化，ＧＯＤ活性有所降低，敞开条件下则活性有所增强，并对其结果进行了初步探讨。     

导电酶膜葡萄糖传感器的研究

酶的固定化是酶电极制作中最关键的一步，有关酶固定化技术已有许多报道［１￣１０］，本文设计了一种用二茂铁修饰的，以戊二醛为交联剂将葡萄糖氧化酶固定在一特殊的导电纸基上的方法，此法制得的酶膜与玻碳电极组成酶电极，在２５℃，ｐＨ＝７磷酸盐缓冲液中，线性范围为０～１２ｍｍｏｌ／Ｌ，有效使用寿命达３０ｄ．由于此电极的制作方便及其可分离性使之易于商品化．     

TDP对铜—甘氨酸络合物催化抗坏血酸有氧氧化动力学的影响

本文考察了在TDP处理后,铜—甘氨酸络合物催化抗坏血酸有氧氧化的动力学规律。发现在该条件下的各类反应遵守米氏规律,其最大反应速率明显升高。并对其反应机理提出了一种解释。