Open AccessAn apyrase from Mimosa pudica contains N 5, N 10‐methenyl tetrahydrofolate and is stimulated by light
Author(s) -
Ghosh Rinku,
Biswas Susweta,
Roy Siddhartha
Publication year - 1998
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1327.1998.2581009.x
Subject(s) - apyrase , chromophore , cofactor , mimosa pudica , enzyme , biochemistry , escherichia coli , biology , ultraviolet light , absorbance , chemistry , photochemistry , chromatography , ecology , gene
An apyrase (NTP/NDPase) implicated in the response of Mimosa pudica to stimuli, such as touch, has been cloned, sequenced and expressed in Escherichia coli . While purifying and characterizing this enzyme, it was observed that a chromophore is associated with it, having absorption in the ultraviolet‐A/blue region of the spectrum. The absorbance maximum of the chromophore, purified from the enzyme complex by gel filtration and HPLC, is around 350 nm. The chromophore has been identified as N 5, N 10‐methenyl tetrahydrofolate (MTHF) by comparing the excitation and emission spectra of synthetic MTHF and the isolated cofactor, and by reconstitution of the enzyme complex with synthetic MTHF. Upon excitation with light (350 nm), an increase of apyrase activity was observed in the purified or reconstituted holoenzyme but not in the apoenzyme. The wavelength dependence of the light stimulation matched well with the fluorescence excitation spectra of the cofactor, MTHF. Possible implications of the results for signal transduction in M. pudica have been discussed.