Se. Berdy et al., Molecular characterization of At5PTase1, an inositol phosphatase capable of terminating inositol trisphosphate signaling, PLANT PHYSL, 126(2), 2001, pp. 801-810
The inositol triyhosphate (IP3)-signaling pathway has been associated with
several developmental and physiological processes in plants, but we current
ly know little about the regulation of this pathway. Inositol 5 ' phosphata
ses (5PTases) are enzymes that remove a 5 ' phosphate from several potentia
l second messengers, including IP3. In catalyzing the removal of a 5 ' phos
yhate from second messenger substrates, 5PTases can act to terminate signal
transduction events. We describe the molecular analysis of At5PTasel, a 5P
Tase gene from Arabidopsis. When expressed transiently in Arabidopsis leaf
tissue or ectopically in transgenic plants, At5PTasel allowed for the incre
ased hydrolysis of I(1,4,5)P-3 and I(1,3,4,5)P-4 substrates. At5PTase1 did
not hydrolyze I(1)P, I(1,4)P-2, or PI(4,5)P-2 substrates. This substrate sp
ecificity was similar to that of the human Type I 5PTase. We identified 14
other potential At5PTase genes and constructed an unrooted phylogenetic tre
e containing putative Arabidopsis, human, and yeast 5PTase proteins. This a
nalysis indicated that the Arabidopsis 5PTases were grouped in two separate
branches of the tree. The multiplicity of At5PTases indicates that these e
nzymes may have different substrate specificities and play different roles
in signal termination in Arabidopsis.