Mechanism of interaction of O-amino-D-serine with sheep liver serine hydroxymethyltransferase

Baskaran, N and Prakash, V and Rao, Appu AG and Radhakrishnan, AN and Savithri, HS and Rao, Appaji N (1989) Mechanism of interaction of O-amino-D-serine with sheep liver serine hydroxymethyltransferase. In: Biochemistry, 28 (25). 9607 -9612.

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Abstract

The mechanism of interaction of 0-amino-D-serine (OADS) with sheep liver serine hydroxymethyltransferase (EC 2.1.2.1) (SHMT) was established by measuring changes in the enzyme activity,absorption spectra, circular dichroism (CD) spectra, and stopped-flow spectrophotometry. OADS was a reversible noncompetitive inhibitor (Ki = 1.8 pM) when serine was the varied substrate. The first step in the interaction of OADS with the enzyme was the disruption of enzyme-Schiff base, characterized by the rapid disappearance of absorbance at 425 nm (6.5 X lo3 M-' s-') and CD intensity at 430 nm. Concomitantly,there was a rapid increase in absorbance and CD intensity at 390 nm. The spectral properties of this intermediate enabled its identification as pyridoxal 5'-phosphate (PLP). These changes were followed by a slow unimolecular step (2 X s-') leading to the formation of PLP-OADS oxime, which was confirmed by its absorbance and fluorescence spectra and retention time on high-performance liquid chromatography. The PLP-OADS oxime was displaced from the enzyme by the addition of PLP as evidenced by the restoration of complete enzyme activity as well as by the spectral properties. The unique feature of the mechanism proposed for the interaction of OADS with sheep liver SHMT was the formation of PLP as an intermediate.

Item Type:	Journal Article
Publication:	Biochemistry
Publisher:	American Chemical Society
Additional Information:	Copyright of this article belongs to American Chemical Society.
Department/Centre:	Division of Biological Sciences > Biochemistry
Date Deposited:	19 Oct 2010 09:06
Last Modified:	19 Oct 2010 09:06
URI:	http://eprints.iisc.ac.in/id/eprint/33210

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