New plant adenosine diphosphate (ADP)-glucose phosphodiesterase, useful for determining sugar nucleotide diphosphate or sulfonucleotides, e.g. for diagnosis

摘要

Plant enzyme (I), designated AGPPase, with ADP-glucose phosphodiesterase activity, is a phosphodiesterase that: (i) catalyzes hydrolysis of ADP-glucose (ADPG) to equimolar amounts of glucose-1-phosphate (G1P) and adenosine monophosphate (AMP) (ii) does not hydrolyze phosphomonoesters (iii) does not require ionic effectors of phosphodiesterases and (iv) hydrolyzes bis-PNPP (p-nitrophenyl phosphate), is new. (I) is: (a) inhibited by molybdate, arsenate and phosphoryl compounds (b) not affected by reducing agents or chelating inhibitors of phosphodiesterase (c) sensitive to weakly basic pH but is stable at pH 4-7.5 (d) resistant to ionic detergents of the sodium dodecylsulfate type and to proteases and (e) recognizes substrates, other than ADPG, that contain phosphodiester or phosphosulfate, hydrolyzing them with Michaelis constant (Km) 4-5 times greater than the Km for ADPG. Independent claims are also included for the following: (1) producing (I) as a soluble isoform (2) test kit for determining sugar-nucleotide diphosphates or sulfonucleotides (3) preparing the starch-bound isoform of (I) (4) producing transgenic plants that overexpress the soluble isoform of (I) and (5) transgenic plants with reduced starch content and high resistance to salinity, produced by method (4).