Inositol hexaphosphate guanosine diphosphate phosphotransferase from Phaseolus aureus

Biswas, S. ; Burman, S. ; Biswas, B. B. (1975) Inositol hexaphosphate guanosine diphosphate phosphotransferase from Phaseolus aureus Phytochemistry, 14 (2). pp. 373-375. ISSN 0031-9422

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Inositol hexaphosphate guanosine diphosphate phosphotransferase which transfers phosphate from inositol hexaphosphate to guanosine diphosphate, synthesizing guanosine triphosphate, has been isolated from germinating mung bean. A purification of 86-fold with 33% recovery has been obtained and the protein was made homogeneous after polyacrylamide gel electrophoresis. The MW of this enzyme was ca 92000. The optimal pH was 7·0 and Mn2+ was stimulatory. Inositol hexaphosphate was the most active donor of the phosphoryl group (P) to GDP. Inositol penta- or tetra-phosphate (mixed) was partially active, but inositol pentaphosphate produced in this reaction did not act further as phosphate donor. The transfer of P from inositol hexaphosphate was mediated through a phosphoprotein. Polyphosphate (poly Pi), pyrophosphate (PPi) and orthophosphate (Pi) were inactive in this reaction. ADP, CDP and UDP could not substitute for GDP, neither could dGDP nor GMP accept P from inositolphosphate. GTP inhibited the reaction, but ATP did not interfere with the reaction. The products have been shown to be [GMP-32P] and inositol pentaphosphate by several criteria. The reaction is practically irreversible. Km values for GDP and inositol hexaphosphate were 1·1 × 10-4 M and 1·6 × 10-6 M respectively.

Item Type:Article
Source:Copyright of this article belongs to Phytochemical Society of Europe.
Keywords:Phaseolus aureus; Leguminosae; Mung Bean; Inositol Hexaphosphate Guanosine Diphosphate Phosphotransferase
ID Code:3554
Deposited On:12 Oct 2010 04:16
Last Modified:19 May 2011 08:11

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