Studies of triose phosphate isomerase by hydrogen exchange.
The (3)H-H exchange of chicken muscle and rabbit muscle triose phosphate isomerases was studied. Their behaviour was mostly very similar. ;Exchange-in' (acquisition of radioactivity when protein was incubated in (3)H(2)O) was measured at 37 degrees C and at pH7.5, and the rates of exchange of the native and liganded enzymes were compared. Inhibitors and substrates retarded exchange, substrates showing the most marked effect; structural rearrangements in the enzyme may thus play some part in catalysis. The inhibitor phosphoglycollate affected the rabbit enzyme, but had little or no effect on the chicken enzyme. ;Exchange-out' (loss of radioactivity from protein previously labelled by incubation in (3)H(2)O) was measured by hollow-fibre dialysis. When ligand was removed during the course of dialysis (by replacing buffer that contained ligand with buffer that lacked ligand) there was a prompt decrease in the number of labelled H atoms of the protein. Analysis of the curves provides some information about the number and half-lives of the responsive H atoms. Ligands decrease the motility of the protein and affect about one-fifth of the chain. Low concentrations of glycerol 3-phosphate have an effect that is greater than expected.
D000818:Animals; D002238:Carbohydrate Epimerases / Q000378:metabolism*; D002384:Catalysis; D002645:Chickens; D003956:Dialysis; D005994:Glycerophosphates; D006859:Hydrogen / Q000378:metabolism*; D008024:Ligands; D009132:Muscles / Q000201:enzymology; D011817:Rabbits; D014306:Trioses; D014316:Tritium
D005994:Glycerophosphates; D008024:Ligands; D014306:Trioses; D014316:Tritium; D006859:Hydrogen; D002238:Carbohydrate Epimerases