Hydron transfer catalyzed by triosephosphate isomerase. Products of isomerization of dihydroxyacetone phosphate in D2O.
The product distributions for the reactions of dihydroxyacetone phosphate (DHAP) in D(2)O at pD 7.9 catalyzed by triosephosphate isomerase (TIM) from chicken and rabbit muscle were determined by (1)H NMR spectroscopy using glyceraldehyde 3-phosphate dehydrogenase to trap the first-formed products of the thermodynamically unfavorable isomerization reaction, (R)-glyceraldehyde 3-phosphate (GAP) and [2(R)-(2)H]-GAP (d-GAP). Three products were observed from the reactions catalyzed by TIM: GAP from isomerization with intramolecular transfer of hydrogen (18% of the enzymatic products), d-GAP from isomerization with incorporation of deuterium from D(2)O into C-2 of GAP (43% of the enzymatic products), and [1(R)-(2)H]-DHAP (d-DHAP) from incorporation of deuterium from D(2)O into C-1 of DHAP (40% of the enzymatic products). The ratios of the yields of the deuterium-labeled products d-DHAP and d-GAP from partitioning of the intermediate of the TIM-catalyzed reactions of GAP and DHAP in D(2)O are 1.48 and 0.93, respectively. This provides evidence that the reaction of these two substrates does not proceed through a single, common, reaction intermediate but, rather, through distinct intermediates that differ in the bonding and arrangement of catalytic residues at the enediolate O-1 and O-2 oxyanions formed on deprotonation of GAP and DHAP, respectively.
O'Donoghue
Annmarie C
AC
Department of Chemistry, University at Buffalo, SUNY, Buffalo, New York 14260-3000, USA.
Amyes
Tina L
TL
Richard
John P
JP
D000818:Animals; D002384:Catalysis; D002645:Chickens; D017666:Deuterium Oxide / Q000737:chemistry*; D004099:Dihydroxyacetone Phosphate / Q000737:chemistry* / Q000378:metabolism; D004735:Energy Transfer; D005986:Glyceraldehyde 3-Phosphate / Q000378:metabolism; D024601:Glyceraldehyde 3-Phosphate Dehydrogenase (NADP+) / Q000378:metabolism; D005988:Glyceric Acids / Q000378:metabolism; D020100:Hydrogels; D009124:Muscle Proteins / Q000737:chemistry* / Q000378:metabolism; D019906:Nuclear Magnetic Resonance, Biomolecular; D011102:Polyhydroxyethyl Methacrylate / Q000031:analogs & derivatives* / Q000378:metabolism*; D011817:Rabbits; D013237:Stereoisomerism; D013379:Substrate Specificity; D014305:Triose-Phosphate Isomerase / Q000737:chemistry* / Q000378:metabolism
D005988:Glyceric Acids; D020100:Hydrogels; D009124:Muscle Proteins; C000257:polyhydroxyethyl methacrylate hydrogels; D005986:Glyceraldehyde 3-Phosphate; D011102:Polyhydroxyethyl Methacrylate; D004099:Dihydroxyacetone Phosphate; C005156:3-phosphoglycerate; D024601:Glyceraldehyde 3-Phosphate Dehydrogenase (NADP+); D014305:Triose-Phosphate Isomerase; D017666:Deuterium Oxide