期刊名称:Proceedings of the National Academy of Sciences
印刷版ISSN:0027-8424
电子版ISSN:1091-6490
出版年度:2007
卷号:104
期号:7
页码:2080-2085
DOI:10.1073/pnas.0608876104
语种:English
出版社:The National Academy of Sciences of the United States of America
摘要:The highly efficient glycolytic enzyme, triosephosphate isomerase, is expected to differentially stabilize the proposed stable reaction species: ketone, aldehyde, and enediol(ate). The identity and steady-state populations of the chemical entities bound to triosephosphate isomerase have been probed by using solid- and solution-state NMR. The 13C-enriched ketone substrate, dihydroxyacetone phosphate, was bound to the enzyme and characterized at steady state over a range of sample conditions. The ketone substrate was observed to be the major species over a temperature range from -60{degrees}C to 15{degrees}C. Thus, there is no suggestion that the enzyme preferentially stabilizes the reactive intermediate or the product. The predominance of dihydroxyacetone phosphate on the enzyme would support a mechanism in which the initial proton abstraction in the reaction from dihydroxyacetone phosphate to D-glyceraldehyde 3-phosphate is significantly slower than the subsequent chemical steps.