Specific modification of free lysine amino groups of histidine decarboxylase from Micrococcus sp. n. by trinitrobenzene sulfonic acid
Semina, L.A.; Gonchar, N.A.; Kharitonenkov, I.G.; Grebenshchikova, O.G.
Biokhimiia 41(12): 2212-2219
1976
ISSN/ISBN: 0320-9725 PMID: 1022283 Document Number: 102408
Fourteen lysine residues are accessible for trinitrobenzene sulfonic acid (TNBS) in the molecule of histidine decarboxylase (HDC). The other 62 lysine residues in the molecule of native HDC are masked and inaccessible for TNBS. The SH- and .alpha.-amino groups of methionine are not modified by TNBS. The correlation between the decarboxylase activity and the degree of trinitrophenylation was studied. HDC, whose molecule contains 3-9 TNP groups, retains up to 90-97% of its initial activity. Trinitrophenylation of 14 lysine residues induces inactivation of HDC by 33-34%, which probably depends on conformational changes or steric hindrances occurring in the catalytic site of the modified active center of HDC. Circular dichroism, fluorescence methods and disc electrophoresis in polyacrylamide gel showed that trinitrophenylation does not cause any significant changes in the enzyme structure. The TNP groups were localized in the large and small subunits of the HDC molecule.