@article {Daniel-Ivad2024-fb,
	title = {An imine reductase that captures reactive intermediates in the biosynthesis of the indolocarbazole reductasporine},
	journal = {J. Biol. Chem.},
	volume = {300},
	number = {2},
	year = {2024},
	pages = {105642},
	publisher = {Elsevier BV},
	abstract = {Imine reductases (IREDs) and reductive aminases have been used in the synthesis of chiral amine products for drug manufacturing; however, little is known about their biological contexts. Here we employ structural studies and site-directed mutagenesis to interrogate the mechanism of the IRED RedE from the biosynthetic pathway to the indolocarbazole natural product reductasporine. Cocrystal structures with the substrate-mimic arcyriaflavin A reveal an extended active site cleft capable of binding two indolocarbazole molecules. Site-directed mutagenesis of a conserved aspartate in the primary binding site reveals a new role for this residue in anchoring the substrate above the NADPH cofactor. Variants targeting the secondary binding site greatly reduce catalytic efficiency, while accumulating oxidized side-products. As indolocarbazole biosynthetic intermediates are susceptible to spontaneous oxidation, we propose the secondary site acts to protect against autooxidation, and the primary site drives catalysis through precise substrate orientation and desolvation effects. The structure of RedE with its extended active site can be the starting point as a new scaffold for engineering IREDs and reductive aminases to intercept large substrates relevant to industrial applications.},
	keywords = {biosynthesis, enzyme catalysis, enzyme structure, imine reductase, indolocarbazole, SITE-DIRECTED MUTAGENESIS, X-RAY CRYSTALLOGRAPHY},
	author = {Daniel-Ivad, Phillip and Ryan, Katherine S}
}
@article {494,
	title = {Mechanistic aspects of enzymatic carbohydrate epimerization},
	journal = {Natural Product Reports},
	volume = {19},
	number = {3},
	year = {2002},
	note = {ISI Document Delivery No.: 566QLTimes Cited: 21Cited Reference Count: 214},
	month = {Jun},
	pages = {261-277},
	type = {Review},
	abstract = {Carbohydrate epimerases are enzymes that catalyze an inversion of stereochemistry at a stereogenic center in a sugar. This review focuses on the mechanistic strategies that are employed by this diverse family of enzymes, and is divided into the following sections: deprotonation/reprotonation, transient oxidation, cofactor independent, and mutarotation. The review is comprehensive up to Oct. 2001 and contains 216 references.},
	keywords = {2-EPIMERASE, ACETYLNEURAMINIC, ACID BIOSYNTHESIS, D-GLUCOSAMINE 2-EPIMERASE, D-MANNOHEPTOSE 6-EPIMERASE, GDP-L-FUCOSE, GLUCURONYL C-5 EPIMERASE, MANNURONAN C-5-EPIMERASE, N-ACETYLGLUCOSAMINE, RENIN-BINDING PROTEIN, SITE-DIRECTED MUTAGENESIS, UDP-GALACTOSE 4-EPIMERASE, VINELANDII},
	isbn = {0265-0568},
	url = {<Go to ISI>://000176439700001},
	author = {Samuel, J. and Tanner, M. E.}
}
@article {5226,
	title = {Reaction of human myoglobin and peroxynitrite: Characterizing biomarkers for myoglobin-derived oxidative stress},
	journal = {Biochemical and Biophysical Research Communications},
	volume = {286},
	number = {2},
	year = {2001},
	note = {ISI Document Delivery No.: 465TNTimes Cited: 11Cited Reference Count: 32},
	month = {Aug},
	pages = {352-356},
	type = {Article},
	abstract = {Mixtures of human myoglobin (Mb) (or the Y103F variant of human Mb), authentic peroxynitrite (ONOO-, ONOO-:protein 2 mol/mol), and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) gave radicals adducts at cysteine-110 (DMPO-C110) that are detected directly by electron paramagnetic magnetic spectroscopy (EPR). DMPO-C110 was detected exclusively over a range of DMPO concentrations (DMPO:protein ratios 25-100 mol/mol). Treatment of human Mb (or Y103F Mb) with the ONOO- generator 5-amino-3-(4-morpholinyl)-1,2,3-oxadiazolium (SIN-1) chloride (ONOO-: protein 5 mol/mol) yielded a cross-linked Mb dimer as judged by SDS-PAGE analyses. Addition of DMPO or carbonate effectively eliminated the cross-linked product. Mass analyses of samples containing human Mb (or Y103F Mb), carbonate, and ONOO- indicated that nitration occurs exclusively at Y103. Thus, reaction of human Mb and ONOO- yields specific products that depend on the presence or absence of physiological concentrations of carbonate. These products may serve as biomarkers for the participation of Mb-derived radicals in the oxidative damage associated with myocardial reperfusion injury. (C) 2001 Academic Press.},
	keywords = {ARRHYTHMIAS, free radical, GENERATION, HYDROGEN-PEROXIDE, ischaemia reperfusion injury, MECHANISMS, MYOGLOBIN, NITRATION, NITRIC-OXIDE, nitro-tyrosine, peroxynitrite, protein-thiyl radical, radicals, REPERFUSION INJURY, SITE-DIRECTED MUTAGENESIS, SUPEROXIDE, SYSTEMS},
	isbn = {0006-291X},
	url = {<Go to ISI>://000170606200020},
	author = {Witting, P. K. and Mauk, A. G. and Douglas, D. J. and Stocker, R.}
}
@article {5208,
	title = {Sugar nucleotide-modifying enzymes},
	journal = {Current Organic Chemistry},
	volume = {5},
	number = {2},
	year = {2001},
	note = {ISI Document Delivery No.: 411FKTimes Cited: 12Cited Reference Count: 170},
	month = {Feb},
	pages = {169-192},
	type = {Review},
	abstract = {Sugar nucleotides serve as the activated forms of carbohydrates that are used in a wide range of biosynthetic pathways. Instead of building up the sugar nucleotide from the free sugar itself, nature often chooses to modify the "donor" portion of a pre-existing sugar nucleotide in a biosynthetically efficient manner. In doing so a rich variety of catalytic strategies are employed and this review focuses on recent mechanistic and structural studies of the sugar nucleotide-modifying enzymes. The review is organized around the types of reactions catalyzed and contains the following sections: Epimerases/Mutases/Decarboxylases, Eliminations and Substitutions, Oxidation and Reduction, and Substitutions on the Periphery of Sugar Nucleotides.},
	keywords = {4, 6-DEHYDRATASE, 6-DIDEOXYHEXOSES, ACETYLGLUCOSAMINE 2-EPIMERASE/N-ACETYLMANNOSAMINE, ACETYLNEURAMINIC ACID, biosynthesis, CYTIDINE DIPHOSPHATE 3, D-GLUCOSE, ESCHERICHIA-COLI K-12, FIRST 2, GDP-FUCOSE SYNTHETASE, KINASE, N-ACETYLGLUCOSAMINE, SITE-DIRECTED MUTAGENESIS, STEPS, UDP-GALACTOSE 4-EPIMERASE},
	isbn = {1385-2728},
	url = {<Go to ISI>://000167487300004},
	author = {Tanner, M. E.}
}
