Essential arginine residues in D-glyceraldehyde-3-phosphate dehydrogenase.

Two arginyl residues per subunit of yeast D-glyceraldehyde-3-phoshphate dehydrogenase were modified by treatment with butanedione without significant changes in the compostion of other amino acid residues. The modified enzyme displays no dehydrogenase activity. It retains the capacity for interacting with the coenzyme NAD, but binds it less firmly than does the native enzyme. The molar absorbance of the enzyme-NAD complex is markedly reduced and the reactivity of the active-center SH groups is changed in the modified enzyme. The native and modified enzymes show identical fluorescence spectra, absorbance and CD spectra.