Identification of a fluorescent dye-containing peptide of glyceraldehyde-3-phosphate dehydrogenase.

The NAD-induced local conformational changes in the fluorescent dye-binding region of muscle glyceraldehyde-3-phosphate dehydrogenase were studied (Ovádi et al., 1982). We have isolated a dominant peptide containing the fluorescent dye from the tryptic digest of labelled dehydrogenase, and identified this labelled amino acid residue. The data indicate that fluorescein isothiocyanate can react rather specifically with tyrosyl residue 91, which is not associated with the catalytic function of the enzyme. Tyrosyl-91 modified by the fluorescent dye does not interact directly with any part of the NAD bound at the active site of glyceraldehyde-3-phosphate dehydrogenase.