Lysine - sensitive aspertate kinase of Serratia marcescens.

Shailaja, M. S. and Raghavendra Rao, M. R. (1975) Lysine - sensitive aspertate kinase of Serratia marcescens. Indian Journal of Biochemistry and Biophysics, 12. pp. 17-20.

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Abstract

Aspartate kinase (EC 2.2.2.7) activity of the bacterium, Serratia marcescens Sa-3, is repressed 10, 60 and 90% by lysine, L-homoserine and methionine respectively. Its repression is complete when the bacterium is growth in the presence of the four amino acids (methionine + lysine + isoleucine + threonine). There is an increase in the specific activity and quantity of the enzyme during exponential growth phase, and a rapid decrease thereafter. The enzyme has been purified 50-fold, but it still contains a protein Impurity (25%). Among the amino acids tested, only L·lysine Inhibits SO and 85% of the enzyme activity of the unfractionated cell-free extracts and the purified enzyme respectively. Lysine inhibition is of the competitive type. The purified enzyme has a rather high Km of 50mM for L-aspartate and 6.9 mMfor ATP. The energy of activation of the enzyme is 16.6 kcal/mole. Potassium ions (upto 0.15 m) stimulate and stabilize the enzyme activity, and Mg2+ ions are the best acthat0l'S amoog lhe divalent cations. The apparent molecular weight of the enzyme is 280000 by the gel filtration procedure. Urea (8M) reduces the activity b)' 60% which is not restored on dialysis. In its specific sensitivity to lysine, the enzyme resembles AK III of Esch. coli K11 and Salmonella typhimurium, one of the two aspartate kinases of Bacillus Sabtilis and the maize shoot enzyme. It, however, differs from the above and the Pseudomonas putida enzyme in its strong repressibility by methionine relative stability in the presence of other amino acids and in tile nature of inhibition by lysine.

Item Type:	Article
Uncontrolled Keywords:	Aspartate kinase, bacterium, Serratia marcescens, lysine
Subjects:	500 Natural Sciences and Mathematics > 07 Life Sciences > 03 Biochemistry & Molecular Biology > 07 Enzyme Biochemistry
Divisions:	Dept. of Biochemistry
Depositing User:	Food Sci. & Technol. Information Services
Date Deposited:	13 Jul 2016 12:40
Last Modified:	13 Jul 2016 12:40
URI:	http://ir.cftri.res.in/id/eprint/4581

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