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PubMed1976

[Specific modification of free lysine amino groups of histidine decarboxylase from Micrococcus sp. n. by trinitrobenzene sulfonic acid].

It has been found that 14 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. It is demonstrated that the SH- and alpha-amino groups of methionine are not modified by TNBS. A correlation between the decarboxylase activity of the enzyme and the degree of its trinitrophenylation has been 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 centre of HDC. Using circular dichroism and fluorescence methods as well as disc-electrophoresis in polyacrylamide gel, it has been shown that trinitrophenylation does not cause any significant changes in the enzyme structure. The TNP groups have been found to be localized in the large and small subunits of the HDC molecule.

Carboxy-Lyases↗
PubMed1976

[Amino acid sequence in tryptic peptides of maleylated Micrococcus sp. n. histidine decarboxylase beta-polypeptide chain].

Maleilated histidine decarboxylase beta-polypeptide chain, containing 3 arginine residue, was hydrolysed by trypsin. 4 non-overlapping homogenous peptides were isolated, 3 of them containing one arginine residue and the 4th peptide being C-terminal fragment of beta-chain. beta-Polypeptide chain is found to consist of 78 amino acid residues and to have molecular weight of 8456. Primary structure of each peptide and their possible sequence in beta-chain are determined.

Amino Acid Sequence↗
PubMedDate not supplied

[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.

Carboxy-Lyases↗
PubMed1975

The presence of an endonuclease acting on UV-irradiated and depurinized DNA in cells of Micrococcus lysodeikticus.

Enzymatic activity, hydrolyzing DNA treated with beta-isopropyl-bis-beta-chloroethylamine (HN2-DNA), HN2-DNA exposed at 50 degrees for 1 h, and DNA treated with acid, to acid-soluble fragments was found in extracts from cells of M. lysodeikticus. The endonucleolytic component ofthe indicated activity manifests chromatographic properties on DEAE- and CM-cellulose, close to those for UV-endonuclease. Activity is manifested by UV-irradiated DNA, proflavin, and cyanide. Two electrophoretically homogeneous fractions of UV-endonuclease (after chromatography on DEAE- and CM-cellulose), with molecular weights about 13,000 and 15,000 daltons, exhibit endonucleolytic activity with respect to HN2-DNA, exposed at 50 degrees for 1 h, and with respect to "acid" DNA, treated for 6 min at 70 degrees in citrate buffer, pH 3.5. The activity with respect to the latter substrate is competitively suppressed by UV-irradiated DNA. The most probable substrate of UV-endonuclease, in addition to cyclobutane dimers, is the depurinized region of DNA.

Apurinic Acid↗