Characterization of Thermophilic Archaeal Isopentenyl Phosphate Kinases
摘要:
Archaea synthesize isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP), the essential building blocks of isoprenoid compounds, from mevalonate (MVA). However, an analysis of the genomes of several members of the Archaea failed to identify genes for the enzymes required to convert phosphomevalonate (PM) to IPP In eukaryotes. The recent discovery of an isopentenyl kinase (IPK) in Methanocaldococcus jannaschii (MJ) Suggests a new variation of the MVA pathway where PM is decarboxylated to give isopentenyl phosphate (IP), which is phosphorylated to produce IPP. A blast search using the MJ protein as a probe revealed a subfamily of amino acid kinases that include the fosfomycin resistance protein fomA, which deactivates the antibiotic by phosphorylation of its phosphonate residue in a reaction similar to the conversion of IP to IPP. IPK genes were cloned from two organisms identified in the search, Methanothermobacter thermautotrophicus (MTH) and Thermoplasma acidophilum (THA), and the His-tagged recombinant proteins were purified by Ni-NTA chromatography. The enzymes catalyze the reversible phosphorylation of IP by ATP, K-cq = 6.3 +/- 1. The catalytic efficiencies (V/K) of the proteins were similar to 2 x 10(6) M-1 s(-1). In the reverse direction, ADP wits a substrate inhibitor for THA IPK, K-i(ADP) = 58 +/- 6 mu M, but not for MTH IPK. Both enzymes were active over a broad range of pH and temperature. Five compounds, dimethylallyl phosphate, isopentenyl thiolophosphate, 1-butyl phosphate, 3-buten-1-yl phosphate, and geranyl phosphate, were evaluated as alternative substrates for the MTH and THA IP kinases. All of the compounds were phosphorylated, although the catalytic efficiency was low for geranyl phosphate.
Phosphate esters of two butanol isomers were synthesized by esterification of n‐butanol and isobutanol with phosphorus pentoxide. The surface activity and penetrability of the esters were analyzed by way of surface chemistry and canvas disc wetting tests in different alkaline solutions. The surface tension of the butanol phosphate esters and their sodium salts was found to decrease with increasing
通过将正丁醇和异丁醇与五氧化二磷酯化来合成两种丁醇异构体的磷酸酯。通过在不同碱性溶液中的表面化学和帆布圆盘润湿测试,分析了酯的表面活性和渗透性。发现丁醇磷酸酯及其钠盐的表面张力随碱浓度增加至250 g / L NaOH而降低。此外,该产品即使在高碱性溶液中也表现出良好的表面活性和适当的渗透性。酯在浓碱液中的稳定表面活性可以归因于由于常见的离子效应而从溶液中吸附分子。