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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 |
URI: | http://hdl.handle.net/123456789/3728 |
ISSN: | 0301-1208 |
Appears in Collections: | IJBB Vol.41(6) [December 2004] |
Files in This Item:
File | Description | Size | Format | |
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IJBB 41(6) 288-293.pdf | 155.12 kB | Adobe PDF | View/Open |
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