宋昊
,
张颖鑫
,
孔维宝
,
夏春谷
催化学报
doi:10.1016/S1872-2067(11)60443-9
The activities of the key enzymes involved in the intracellular poly-3-hydroxybutyrate (PHB) synthesis of Methylosinus trichosporium IMV3011 were studied under various cultivation conditions. The enzymes were methane monooxygenase (MMO),β-ketothiolase, acetoacetyl-CoA reductase, PHB synthetase, and PHB depolymerase. Each enzyme had a unique catalytic mechanism. MMO activity decreased continuously with PHB production, but PHB at a high concentration was beneficial for maintaining MMO activity because more NADH was released by PHB depolymerization. The important reaction for entering the PHB cycle was catalyzed byβ-ketothiolase. The monomer of β-hydroxybutyrate was synthesized by the catalysis of β-ketothiolase and acetoacetyl-CoA reductase. PHB synthetase played an important role in the PHB synthesis routes. The activity of PHB synthetase increased with PHB production. The changes of en-zyme activities involved in PHB synthetase and PHB depolymerase occurred together, which indicated that the polymerization and depoly-merization of intracellular PHB occurred simultaneously. The molecular weight of PHB was determined mainly by the combined actions of PHB synthetase and PHB depolymerase. Some important intermediates in the tricarboxylic acid cycle were helpful for PHB production be-cause they increased related enzyme activities in the PHB cycle.
关键词:
enzyme activity
,
biocatalysis
,
poly-3-hydroxybutyrate
,
methanotrophic bacteria
王梦亮
,
闫甫昆
催化学报
doi:10.3724/SP.J.1088.2010.90801
将类球红杆菌(Rhodobacter sphaeroides)全细胞及其分离得到的羰基还原酶用于不对称催化还原多种潜手性酮类化合物,通过比较产物的收率、ee值、酶活力以及酶学动力学常数K_m,探讨了类球红杆菌的催化还原性质与底物结构的关系.结果表明,对于类球红杆菌全细胞不对称催化还原苯乙酮衍生物,产物ee值的变化遵循Prelg规则,产物收率与底物苯环及侧链上取代基团的性质有关;对于脂肪酮催化还原,产物收率随底物链长的增加和分子量的增大而降低,随支链数日的增加而升高,产物ee值的变化也遵循Prelg规则.利用羰基还原酶不对称催化还原潜手性酮类化合物发现,对于芳香酮类化合物,酶对α位为强电负性基团的底物专一性较强;对于脂肪酮类化合物,酶对五碳脂肪酮的专一性较高.利用酶直接催化还原反应产物的ee值均为99%左右,表明酶较全细胞有更高的立体选择性.
关键词:
类球红杆菌
,
生物催化
,
羰基还原酶
,
苯乙酮
,
衍生物
,
脂肪酮
,
构效关系
王净
,
田晶
,
许建和
催化学报
以对甲基苯甲酸为唯一碳源筛选能够生物催化合成对苯二甲酸的菌株,发现只有睾丸酮丛毛单胞菌DSM6577可以氧化对甲基苯甲酸生成对苯二甲酸. 对该菌株的细胞生长及其催化对甲基苯甲酸转化为对苯二甲酸的过程进行了研究. 结果表明,底物在8 h内即可完全转化,产物的生成时间为14～31 h, 其中在21 h时产量最大,为34 mg/L.
关键词:
睾丸酮丛毛单胞菌
,
生物催化
,
对甲基苯甲酸
,
对苯二甲酸
