Nontargeted in vitro metabolomics for high-throughput identification of novel enzymes in Escherichia coli
作者:Daniel C Sévin、Tobias Fuhrer、Nicola Zamboni、Uwe Sauer
DOI:10.1038/nmeth.4103
日期:2017.2
A method to screen proteins for enzymatic activity by incubating purified or overexpressed proteins with a metabolite extract and measuring changes in metabolite abundance using mass spectrometry enables high-throughput characterization of functionally uncharacterized proteins in Escherichia coli. Our understanding of metabolism is limited by a lack of knowledge about the functions of many enzymes. Here, we develop a high-throughput mass spectrometry approach to comprehensively profile proteins for in vitro enzymatic activity. Overexpressed or purified proteins are incubated in a supplemented metabolome extract containing hundreds of biologically relevant candidate substrates, and accumulating and depleting metabolites are determined by nontargeted mass spectrometry. By combining chemometrics and database approaches, we established an automated pipeline for unbiased annotation of the functions of novel enzymes. In screening all 1,275 functionally uncharacterized Escherichia coli proteins, we discovered 241 potential novel enzymes, 12 of which we experimentally validated. Our high-throughput in vitro metabolomics method is generally applicable to any purified protein or crude cell lysate of its overexpression host and enables performing up to 1,200 nontargeted enzyme assays per working day.
The pyrimidine nucleoside phosphorylase (Py-NPase) of Bacillus stearothermophilus TH 6–2 is a dimer of 46-kDa subunits and catalyzes the reversible phosphorolysis of uridine and thymidine. The gene encoding this pyrimidine nucleoside phosphorylase (pyn gene) has been cloned and sequenced from B. stearothermophilus TH 6–2. The pyn gene corresponded to an open reading frame of 1299 nucleotides that translates into a putative 433 amino acid protein with a molecular weight of 46,271. The deduced amino terminal sequence of Py-NPase coincided with that previously found for the purified enzyme. The deduced amino acid sequence of Py-NPase shared significant similarity with those of human and Escherichia coli thymidine phosphorylases. The cloned pyn gene was overexpressed in E. coli cells to produce an active enzyme in large quantities that accounted for approximately 20% of the total protein.
Purification and Characterization of Purine Nucleoside Phosphorylase and Pyrimidine Nucleoside Phosphorylase from<i>Bacillus stearothermophilus</i>TH 6-2
The purine nucleoside phosphorylase (Pu-NPase) and the pyrimidine nucleoside phosphorylase (Py-NPase) have been purified from Bacillus stearothermophilus TH 6–2. The Pu-NPase is a trimer of 30-kDa subunits and the Py-NPase is a dimer of 46-kDa subunits. The isoelectric points of Pu-NPase and Py-NPase were pH 4.3 and 4.6, respectively. The Pu-NPase could catalyze the phosphorolysis of inosine and guanosine, but not adenosine. The Py-NPase could phosphorolyze both uridine and thymidine.
The crystal structure of pyrimidine nucleoside phosphorylase in a closed conformation
作者:Matthew J Pugmire、Steven E Ealick
DOI:10.1016/s0969-2126(98)00145-2
日期:1998.11
undergoes a major conformational change upon substrate binding that consequently produces an active conformation. RESULTS The crystalstructure of PYNP from B. stearothermophilus with the substrate analog pseudouridine in its active site has been solved to 2.1 A resolution. This structure confirms the similarity of PYNP to TP and supports the idea of a closed active conformation, which is the result