[Flourescent properties of histidine decarboxylase from Micrococcus sp. n]

A dependency of fluorescence parameters of histidinedecarboxylase (HDC) from Micrococcuc sp. n. on pH values is studied. Native HDS has a short-waved maximum position (325 nm) and a small half-width of the fluorescence spectrum (48nm). The change in the quantum yield of the enzyme fluorescence was parallel with the change of the enzymatic activity. Triptophane residues of native HDC are located at hydrophobic region of the enzyme globula. The dependency of HDC flourescence parameters on pH values in 8 M urea was similar to that of free triptophane. A comparative study of fluorescences parameters of HDC and its inhibitory complexes with methyl ester of histidine (MEH), hydroxylamine and p-chloromercuriumbensoate is carried out. The effect of HDC interacting with inhibitors on fluorescence parameters of the enzyme is discussed. No differences were found in infra-red spectra of HDC and its inhibitory complex with MEH.