γ-丁基甜菜碱羟基化中的解偶联和同位素效应。
Uncoupling and isotope effects in gamma-butyrobetaine hydroxylation.
作者信息
Holme E, Lindstedt S, Nordin I
出版信息
Biosci Rep. 1984 May;4(5):433-40. doi: 10.1007/BF01122509.
Replacement of unlabeled gamma-butyrobetaine with gamma-[2,3,4-2H6]butyrobetaine has a profound effect on the stoichiometry between decarboxylation of 2-oxoglutarate and hydroxylation in the reaction catalyzed by human gamma-butyrobetaine hydroxylase. The ratios between decarboxylation and hydroxylation are 1.16 with unlabeled and 7.48 with deuterated gamma-butyrobetaine as substrate. From these ratios an internal isotope effect of 41 has been calculated. DV in the overall reaction measured as 2- oxoglutarate decarboxylation is 2.5 and DV/K is 1.0. For gamma-butyrobetaine hydroxylase from Pseudomonas sp. AK 1, 2-oxoglutarate decarboxylation exceeds hydroxylation with 10% when deuterated gamma-butyrobetaine is used. No excess was found with unlabeled substrate and no internal isotope effect could be calculated. DV for the bacterial enzyme is 6.
用人γ-丁基甜菜碱羟化酶催化的反应中，用γ-[2,3,4-2H₆]丁基甜菜碱替代未标记的γ-丁基甜菜碱，对2-氧代戊二酸脱羧与羟化之间的化学计量关系有深远影响。以未标记的γ-丁基甜菜碱为底物时，脱羧与羟化的比率为1.16，以氘代γ-丁基甜菜碱为底物时该比率为7.48。根据这些比率计算出的内在同位素效应为41。以2-氧代戊二酸脱羧衡量的总反应中的DV为2.5，DV/K为1.0。对于来自假单胞菌属AK 1的γ-丁基甜菜碱羟化酶，当使用氘代γ-丁基甜菜碱时，2-氧代戊二酸脱羧超过羟化10%。使用未标记的底物时未发现过量，且无法计算内在同位素效应。该细菌酶的DV为6。
Zotero 插件