Overexpression and characterization of dimeric and tetrameric forms of recombinant serine hydroxymethyltransferase from Bacillus stearothermophilus

Jala, Venkatakrishna R and Prakash, V and Rao, Appaji N and Savithri, HS (2002) Overexpression and characterization of dimeric and tetrameric forms of recombinant serine hydroxymethyltransferase from Bacillus stearothermophilus. In: Journal of Biosciences, 27 (3). pp. 233-242.

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Abstract

Serine hydroxymethyltransferase (SHMT), a pyridoxal-5'-phosphate (PLP) dependent enzyme catalyzes the interconversion of L-Ser and Gly using tetrahydrofolate as a substrate. The gene encoding for SHMT was amplified by PCR from genomic DNA of Bacillus stearothermophilus and the PCR product was cloned and overexpressed in Escherichia coli. The purified recombinant enzyme was isolated as a mixture of dimer (90%) and tetramer (10%). This is the first report demonstrating the existence of SHMT as a dimer and tetramer in the same organism. The specific activities at 37°C of the dimeric and tetrameric forms were 6×7 U/mg and 4×1 U/mg, respectively. The purified dimer was extremely thermostable with a Tm of 85°C in the presence of PLP and L-Ser. The temperature optimum of the dimer was 80°C with a specific activity of 32×4 U/mg at this temperature. The enzyme catalyzed tetrahydrofolate-independent reactions at a slower rate compared to the tetrahydrofolate-dependent retro-aldol cleavage of L-Ser. The interaction with substrates and their analogues indicated that the orientation of PLP ring of B. stearothermophilus SHMT was probably different from sheep liver cytosolic recombinant SHMT (scSHMT).

Item Type:	Journal Article
Publication:	Journal of Biosciences
Publisher:	Indian Academy of Sciences
Additional Information:	Copyright of this article belongs to Indian Academy of Sciences.
Keywords:	Oligomeric structure;orientation of pyridoxal 5 phosphate;serine hydroxymethyltransferase;thermal stability
Department/Centre:	Division of Biological Sciences > Biochemistry
Date Deposited:	30 Oct 2007
Last Modified:	19 Sep 2010 04:40
URI:	http://eprints.iisc.ac.in/id/eprint/12348

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