Biosynthesis of Di-myo-inositol-1,1'-phosphate, a novel osmolyte in hyperthermophilic archaea.
Biosynthesis of di-myo-inositol-1,1'-phosphate (DIP) is proposed to occur with myo-inositol and myo-inositol 1-phosphate (I-1-P) used as precursors. Activation of the I-1-P with CTP and condensation of the resultant CDP-inositol (CDP-I) with myo-inositol then generates DIP. The sole known biosynthetic pathway of inositol in all organisms is the conversion of D-glucose-6-phosphate to myo-inositol. This conversion requires two key enzymes: L-I-1-P synthase and I-1-P phosphatase. Enzymatic assays using 31P nuclear magnetic resonance spectroscopy as well as a colorimetric assay for inorganic phosphate have confirmed the occurrence of L-I-1-P synthase and a moderately specific I-1-P phosphatase. The enzymatic reaction that couples CDP-I with myo-inositol to generate DIP has also been detected in Methanococcus igneus. 13C labeling studies with [2,3-13C]pyruvate and [3-13C]pyruvate were used to examine this pathway in M. igneus. Label distribution in DIP was consistent with inositol units formed from glucose-6-phosphate, but the label in the glucose moiety was scrambled via transketolase and transaldolase activities of the pentose phosphate pathway.
Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02167, USA.
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D002474:Cell-Free System / Q000378:metabolism; D003570:Cytidine Triphosphate / Q000378:metabolism; D006358:Hot Temperature; D007294:Inositol / Q000378:metabolism; D007295:Inositol Phosphates / Q000096:biosynthesis* / Q000378:metabolism; D017017:Methanococcus / Q000378:metabolism*; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D013237:Stereoisomerism
D007295:Inositol Phosphates; C075843:di-myo-inositol-1,1'-phosphate; C002647:inositol 1-phosphate; D007294:Inositol; D003570:Cytidine Triphosphate