Resonance Raman studies of pyrocatechase-inhibitor complexes

Area of Science:

• Biochemistry
• Spectroscopy
• Protein Chemistry

Background:

• Pyrocatechase is an iron-tyrosinate enzyme crucial for aromatic compound metabolism.
• Understanding the coordination environment of the active-site iron is key to elucidating enzyme function.
• Iron-tyrosinate proteins often feature tyrosine residues ligated to the metal center.

Purpose of the Study:

• To investigate the coordination environment of the active-site iron in pyrocatechase using resonance Raman spectroscopy.
• To differentiate and characterize the tyrosine residues coordinated to the iron center.
• To explore the influence of benzoate and phenolate binding on the enzyme's active site.

Main Methods:

• Resonance Raman spectroscopy was employed.
• Argon and krypton laser lines were used for excitation.
• Spectra of native pyrocatechase and its benzoate/phenolate complexes were analyzed.

Main Results:

• Evidence for two distinct tyrosines coordinated to the active-site iron was obtained.
• The two tyrosines exhibited different carbonyl (upsilon CO) stretching frequencies.
• Maximum resonance enhancements occurred at different excitation wavelengths for each tyrosine.
• One tyrosine showed greater susceptibility to changes in the active-site environment.

Conclusions:

• Pyrocatechase is a unique iron-tyrosinate protein where the iron-ligating tyrosines are distinguishable.
• The distinct spectral properties suggest differential roles or environments for these tyrosines.
• These findings provide insights into the structural and functional mechanisms of pyrocatechase.