title: Uncoupling and isotope effects in gamma-butyrobetaine hydroxylation.
abstract: 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.
mesh_terms: D001622:Betaine / Q000031:analogs & derivatives* / Q000378:metabolism; D002245:Carbon Dioxide / Q000096:biosynthesis; D002331:Carnitine / Q000096:biosynthesis; D006801:Humans; D007668:Kidney / Q000201:enzymology; D007700:Kinetics; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D013379:Substrate Specificity; D014316:Tritium; D050563:gamma-Butyrobetaine Dioxygenase
chemical_list: D014316:Tritium; D002245:Carbon Dioxide; D001622:Betaine; C002889:gamma-butyrobetaine; D006899:Mixed Function Oxygenases; D050563:gamma-Butyrobetaine Dioxygenase; D002331:Carnitine