By the UV difference spectrum and fluorescence spectrum technique, the tyrosine environment of flammulin was studied and the results show a typical maximal UV absorption peak of tyrosine residues in flammulin at 275nm, with ε~ m~a~x=20322 L·mol^-^1·cm^-^1. According to the results of the UV difference spectrophotometric titration, the UV difference absorption △A~2~9~4~.~4~n~m shows close correlation to pH ranging from 10.1 to 12.5. The titration curve of tyrosine shows that the apparent dissociation constant pK~a' of tyrosine is 11.4. Since no tryptophane is found in flammulin, the protein only shows the fluorescence of tyrosine residues. The fluorescence spectrum of flammulin shows that the maximal emission wavelength is at 305nm when excited at 280nm, which is sensitive to SDS and ph and quenchable by acrylamide but not by KI. The results indicate that the tyrosine residues of flammulin reside in the hydrophobic core, and the tyrosine residues, together with other hydrophobic amino acid residues in flammulin, form a stable non-polar hydrophobic environment.

Key words: TYROSINE, FLUOROSPECTROPHOTOMETRY