@article {49729,
	title = {Systems-Wide Prediction of Enzyme Promiscuity Reveals a New Underground Alternative Route for Pyridoxal 5{\textquoteright}-Phosphate Production in E. coli.},
	journal = {PLoS Comput Biol},
	volume = {12},
	year = {2016},
	month = {2016 Jan},
	pages = {e1004705},
	abstract = {<p>Recent insights suggest that non-specific and/or promiscuous enzymes are common and active across life. Understanding the role of such enzymes is an important open question in biology. Here we develop a genome-wide method, PROPER, that uses a permissive PSI-BLAST approach to predict promiscuous activities of metabolic genes. Enzyme promiscuity is typically studied experimentally using multicopy suppression, in which over-expression of a promiscuous {\textquoteright}replacer{\textquoteright} gene rescues lethality caused by inactivation of a {\textquoteright}target{\textquoteright} gene. We use PROPER to predict multicopy suppression in Escherichia coli, achieving highly significant overlap with published cases (hypergeometric p = 4.4e-13). We then validate three novel predicted target-replacer gene pairs in new multicopy suppression experiments. We next go beyond PROPER and develop a network-based approach, GEM-PROPER, that integrates PROPER with genome-scale metabolic modeling to predict promiscuous replacements via alternative metabolic pathways. GEM-PROPER predicts a new indirect replacer (thiG) for an essential enzyme (pdxB) in production of pyridoxal 5{\textquoteright}-phosphate (the active form of Vitamin B6), which we validate experimentally via multicopy suppression. We perform a structural analysis of thiG to determine its potential promiscuous active site, which we validate experimentally by inactivating the pertaining residues and showing a loss of replacer activity. Thus, this study is a successful example where a computational investigation leads to a network-based identification of an indirect promiscuous replacement of a key metabolic enzyme, which would have been extremely difficult to identify directly.</p>},
	issn = {1553-7358},
	doi = {10.1371/journal.pcbi.1004705},
	author = {Oberhardt, Matthew A and Zarecki, Raphy and Reshef, Leah and Xia, Fangfang and Duran-Frigola, Miquel and Schreiber, Rachel and Henry, Christopher S and Ben-Tal, Nir and Dwyer, Daniel J and Gophna, Uri and Ruppin, Eytan}
}
