title: Reactions of D-glyceraldehyde 3-phosphate dehydrogenase facilitated by oxidized nicotinamide-adenine dinucleotide.
abstract: Transient kinetic methods have been used to study the influence of NAD(+) on the rate of elementary processes of the reversible oxidative phosphorylation of d-glyceraldehyde 3-phosphate catalysed by d-glyceraldehyde 3-phosphate dehydrogenase. In the pH range 5-8 NAD(+) is bound to the enzyme during the following elementary processes of the mechanism: phosphorolysis of the acyl-enzyme, its formation from 1,3-diphosphoglycerate and the enzyme and the formation and breakdown of the glyceraldehyde 3-phosphate-enzyme complex. The rates of these four elementary processes only equal or exceed the turnover rate of the enzyme when NAD(+) is bound and are as much as 10(4) times the rates in the absence of NAD(+). Autocatalysis of the reductive dephosphorylation of 1,3-diphosphoglycerate occurs when glyceraldehyde 3-phosphate release is rate determining because NAD(+) is a reaction product. An important feature of the enzyme mechanism is that the negative-free-energy change of a chemical reaction, acyl-enzyme formation, is linked in a simple way to the positive-free-energy change of a dissociation reaction, NAD(+) release.
mesh_terms: D000818:Animals; D001665:Binding Sites; D005399:Fishes; D005985:Glyceraldehyde; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D007700:Kinetics; D008956:Models, Chemical; D009132:Muscles / Q000201:enzymology; D009243:NAD; D008121:Nephropidae; D010085:Oxidative Phosphorylation; D013053:Spectrophotometry
chemical_list: D009243:NAD; D005985:Glyceraldehyde; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases