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Indian Journal of Biochemistry and Biophysics (IJBB) >
IJBB Vol.41 [2004] >
IJBB Vol.41(6) [December 2004] >
| Title: | Partial purification, characterization and properties of two isoforms of glutamine synthetase from Pennisetum glaucum L. leaves |
| Authors: | Ghosh, Shilpi |
| Keywords: | Pennisetum glaucum leaves
glutamine synthetase
chloroplastic
isozymes |
| Issue Date: | Dec-2004 |
| Publisher: | CSIR |
| IPC Code: | C12N 9
00 |
| Abstract: | Two isozymes of glutamine synthetase GS1 and GS2 were partially purified from Pennisetum glaucum leaves by ion-exchange and gel filtration chromatography and their kinetic and regulatory properties were studied using semisynthetase assay of GS. Mg2+ was the most effective cation for activity of both the isozymes; however, it could be efficiently replaced by Co 2+.The pH optima for GS1 and GS2 were 7.0 and 8.0, respectively. GS1 exhibited maximum activity at 42ºC, with activation energy of 18 KJ mol-1 and a Q10 of 3.0, whereas GS2 showed maximum activity at 50ºC, with activation energy of 40 KJ mol-1 and Q10 of 2.25. GS1 was more thermostable than GS2. The Km value for Mg2+ of GS1 was 2-fold higher than GS2; however, these isozymes did not differ much in their affinity for other substrates. Alanine, serine and glycine lowered GS1 and GS2 activities, whereas cysteine enhanced their activities with a more pronounced effect on GS2. Serine inhibited the activity of both the isoforms in a competitive-manner, whereas alanine was a non-competitive inhibitor, with respect to glutamate. AMP and ADP were competitive inhibitor with respect to ATP for both the isozymes. |
| Page(s): | 288-293 |
| ISSN: | 0301-1208 |
| Source: | IJBB Vol.41(6) [December 2004]
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