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Lysine - sensitive aspertate kinase of Serratia marcescens.

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Title Lysine - sensitive aspertate kinase of Serratia marcescens.
 
Creator Shailaja, M. S.
Raghavendra Rao, M. R.
 
Subject 07 Enzyme Biochemistry
 
Description 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.
 
Date 1975
 
Type Article
PeerReviewed
 
Format application/pdf
 
Language en
 
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Identifier http://ir.cftri.com/4581/1/Indian%20Journal%20of%20Biochemistry%20and%20Biophysics%2C%20Volume-12%28%20%281975%29%2017-20.pdf
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.