Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.1.99.3 (PRE)
 1,923 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Escherichia coli DNA photolyase contains a stable flavin radical that is readily photoreduced in the presence of added electron donors. Picosecond, nanosecond, and conventional flash photolysis technique have been employed to investigate the events leading to photoreduction from 40 ps to tens of milliseconds following flash excitation. Direct light absorption by the flavin radical produces the first excited doublet state which undergoes rapid (within 100 ps) intersystem crossing to yield the lowest excited quartet (n pi*) state. In contrast, light absorption by the folate chromophore produces a new intermediate state via interaction of the folate excited singlet state with the ground-state flavin radical, leading to an enhanced yield of the excited radical doublet state and hence quartet state. Subsequent reaction of the excited quartet state involves hydrogen atom abstraction from a tryptophan residue. Secondary electron transfer from added electron donors occurs to the oxidized tryptophan radical with rate constants ranging from 10(4) (dithiothreitol) to 4 x 10(6) M-1 s-1 (n-propyl gallate). The low value of the latter rate compared to reduction of the tryptophan radical in lysozyme suggests that the reactive tryptophan is highly buried in photolyase. A redox potential diagram has been constructed for the ground and excited states involved. It is concluded that the one-electron reduction potential of the excited quartet state of the flavin radical must be at least 1.23 V more positive than the ground state, in agreement with the value of delta E greater than 1.77 V calculated from spectroscopic data.
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PMID:Excited-state properties of Escherichia coli DNA photolyase in the picosecond to millisecond time scale. 220 May 10

Microbial cultures produce complex and potentially interesting mixtures of biosynthetic intermediates and derivatives of metabolites. These mixtures' reliable identification is important and so too is the development of techniques for their analysis. Here, a simple and highly selective method of detecting the biosynthetic congeners involved in the pentangular polyphenol pradimicin (PR) pathway from Actinomadura hibisca fermentation was developed. Solid-phase extraction (SPE) cleanup using an OASIS HLB cartridge was a simple and reliable tool for the extraction of PRs from a fermentation broth. The separation of each natural PR analog--eluted with a gradient system of aqueous acetonitrile through a reversed-phase C(18) column containing ammonium acetate and acetic acid as additives--allowed their simultaneous profiling. The combined use of SPE cleanup and chromatographic separation, coupled with electrospray ionization-tandem mass spectrometry (ESI-MS/MS) detection was demonstrated to be sufficiently accurate and reliable to analyze the natural PR analogs produced from A. hibisca. Ten natural PRs were identified: four alanine-containing (PRA, PRC, PRL, and PRB), two glycine-substituted (PRD and PRE), and four serine-substituted (PRFA-1, PRFA-2, PRFL, and PRFB). This report demonstrates the first use of both SPE cleanup and HPLC-ESI-MS/MS to profile a wide range of structurally closely related PRs in a bacterial fermentation broth.
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PMID:Characterization and identification of pradimicin analogs from Actinomadura hibisca using liquid chromatography-tandem mass spectrometry. 2137 31