Purification and properties of myo-inositol-1-phosphatase from bovine brain

Abstract

myo-Inositol-1-phosphatase from bovine brain was purified over 2000-fold. The native enzyme has a Mr of 59,000, and on SDS/polyacrylamide-gel electrophoresis the subunit Mr was 31,000. Thus the native enzyme is a dimer of two apparently identical subunits. The enzyme, purified to a specific activity of more than 300 units/mg of protein (1 unit of enzyme activity corresponds to the release of 1 mumol of Pi/h at 37 degrees C), catalysed the hydrolysis of a variety of phosphorylated compounds, the best one, in terms of V/Km, being D-myo-inositol 1-phosphate. Kinetic constants of compounds tested, including both isomers of glycerophosphate and two deoxy forms of beta-glycerophosphate, were measured. They show the importance of the two hydroxyl groups which are adjacent to the phosphate in myo-inositol 1-phosphate. With a wide variety of substrates Li+ was found to be an uncompetitive inhibitor whose Ki varied with substrate structure.

Occurrence of myo-inositol-1-phosphate phosphatase in pteridophytes: characteristics of the enzyme from the reproductive pinnules of Dryopteris filix-mas (L.) Schott

“…Chhetri et al (2005Chhetri et al ( , 2006 have already established the occurrence of the prime enzyme of myo-inositol biosynthesis, MIPS, in pteridophytes. Therefore, the presence of MIPP adds (Eisenberg Jr. 1967, Attwood et al, 1988Gee et al, 1988;Honchar et al, 1989;Leech et al, 1993;Pollack et al, 1994;Caselli et al, 1996, Fujimoto et al, 1996, Nigou and Besra, 2002Wang et al, 2006;Patra et al, 2007). However, its kinetic parameter, thermo-tolerance and calciumdependent inhibition at lower concentrations, differ substantially in pteridophytic species.…”

“…In pteridophytes, Benaroya et al (2004) and Chettri et al (2005Chettri et al ( , 2006 have recently documented the occurrence and characterization of L-myo-inositol-1-phosphate synthase. So far, work with regard to the participation of the subsequent enzyme in this metabolic sequence, myo-inositol-1-phosphate phosphatase (MIPP), has been carried out principally in animal systems (Eisenberg Jr, 1967;Attwood et al, 1988;Gee et al, 1988;Honchar et al, 1989;Leech et al, 1993;Pollack et al, 1994;Kwok and Lo, 1994;Fujimoto et al, 1996;Caselli et al, 1996), in archaea (Wang et al, 2006), in bacteria (Nigou and Besra, 2002), and in cyanobacteria (Patra et al, 2007). However, only a few reports are available of this enzyme from plant systems (Loewus and Loewus, 1983;Gumber et al, 1984).…”

Histamine‐induced inositol phosphate accumulation in HeLa cells: lithium sensitivity

“…Neither inositol 2-phosphate nor inositol 1:2 cyclic phosphate are substrates for the monophosphatase enzyme in mammalian brain (Shears, 1989, but see Attwood et al, 1988), but whether they are present to any appreciable extent in HeLa cells prelabelled for 20-24 h with [3H]-inositol remains to be established. In brain slices increasing the concentration of Li+ also leads to inhibition of the enzyme inositol polyphosphate 1-phosphatase, which removes the 1-phosphate from inositol 1,4-bisphosphate and inositol 1,3,4-trisphosphate.…”

Spatial Expression Patterns and Biochemical Properties Distinguish a Second myo-Inositol Monophosphatase IMPA2 from IMPA1

“…Biochemical and x-ray crystallographic studies on IMPA1 show that the protein forms homodimers (16,26). Because IMPA2 displayed strong amino acid homology (54%) with IMPA1 (Fig.…”