ring cleavage between carbon 5 and 6, further conversion to formic and maleamic acid is catalyzed by the NicD protein, a deformylase similar to some members of the alpha/beta-hydolase fold superfamily
a series of combined quantum mechanics and molecular mechanics (QM/MM) calculations is performed to illuminate the catalytic mechanism of 2,5-dihydroxypyridine dioxygenase (NicX). On the basis of the calculations, the most plausible reaction pathway and the structures of transition states and intermediates involved in the reaction, as well as the energy profiles, are described in detail
two key factors may influence the substrate specificity of the enzyme (NicX): 1. the successful binding of substrates in the active center, in which the pocket residues, including His189, His105, and Glu177, play a key role in substrate recognition, 2. the activation of the substrate by electron transfer from the substrate to dioxygen. Based on the crystal structure of the 2,5-dihydroxypyridine dioxygenase (NicX), an enzyme-substrate complex model is constructed and QM/MM calculations are carried out to unravel the mechanism of NicX-catalyzed heterocyclic ring cleavage involved in the biochemical degradation of nicotine
ring cleavage between carbon 5 and 6, further conversion to formic and maleamic acid is catalyzed by the NicD protein, a deformylase similar to some members of the alpha/beta-hydolase fold superfamily
ring cleavage between carbon 5 and 6, further conversion to formic and maleamic acid is catalyzed by the NicD protein, a deformylase similar to some members of the alpha/beta-hydolase fold superfamily
ring cleavage between carbon 5 and 6, further conversion to formic and maleamic acid is catalyzed by the NicD protein, a deformylase similar to some members of the alpha/beta-hydolase fold superfamily
one mole per mole enzyme, activation of enzyme with 0.5 mM FeSO4 for 15 min at 25°C, replacement with other divalent cations do not lead to detectable 2,5-dihydroxypyridine dioxygenase activity
purified enzyme is inactive, Fe2+-dependent reactivation of the purified enzyme (0.025 mM), 0.0198 mM iron is detected, indicating that the ratio of mol of iron to mol of a monomer of NicX is near 1.0
1 * 39000, amino acid sequence similarity to aminopeptidase S from Staphylococcus aureus and aminopeptidase T from Thermus thermophilus, 2 globular domains
1 * 39000, amino acid sequence similarity to aminopeptidase S from Staphylococcus aureus and aminopeptidase T from Thermus thermophilus, 2 globular domains
hanging-drop vapor-diffusion method at 20°C, crystal structure for the resting form of the enzyme (NicX), as well as a complex structure wherein 2,5-hydroxy-pyridine and N-formylmaleamic acid are trapped in different subunits. The resting state structure displays an octahedral coordination for Fe(II) with two histidine residues (His265 and His318), a serine residue (Ser302), a carboxylate ligand (Asp320), and two water molecules. 2,5-Hydroxy-pyridine does not bind as a ligand to Fe(II), yet its interactions with Leu104 and His105 function to guide and stabilize the substrate to the appropriate position to initiate the reaction
purified recombinant NicX, hanging drop vapour diffusion method, 0.001 ml of 14 mg/ml protein in 20 mM HEPES pH 7.5, 0.1 M NaCl, and 2 mM DTT, is mixed with 0.001 ml of reservoir solution, containing 22% w/v PEG 4000, 0.1 M sodium acetate and 0.1 M HEPES pH 7.5, 2 mM DTT, and with 1 ml 50 mM EDTA, 18°C, method optimization, X-ray diffraction structure determination and analysis at 2.0 A resolution
nic gene cluster knockout mutants do not grow on nicotinic acid as sole carbon source in contrary to the wild-type, this ability can be restored by introducing a broad-host-range plasmid harboring a 14 kb DNA cassette containing the complete nice cluster, NicX knockout mutant does not show 2,5DHP dioxygenase activity
nic gene cluster knockout mutants do not grow on nicotinic acid as sole carbon source in contrary to the wild-type, this ability can be restored by introducing a broad-host-range plasmid harboring a 14 kb DNA cassette containing the complete nice cluster, NicX knockout mutant does not show 2,5DHP dioxygenase activity
L-cysteine: enzyme has a specific requirement for L-cysteine, 6.7 mM, required to restore full activity after dialysis or treatment with chelating agents
Escherichia coli cells overexpressing NicX are harvested and disrupted by passage through a French press, supernatant applied to DEAE-cellulose column with 50 mM NaH2PO4 buffer, pH 7.5, washed with buffer (0.1-0.3 M) containing 0.1 M NaCl, fraction with 2,5-dihydroxypyridine deoxygenase activity pooled and dialyzed with 20 mM NaH2PO4 buffer, pH 7.5, loaded onto hydroxyapatite column, eluted with 20-100 mM NaH2PO4 buffer, pH 7.0, fractions with enzyme activity pooled, dialyzed in 20 mM NaH2PO4 buffer, pH 7.5, and concentrated
PCR-amplification of nicX gene, overexpression of nix gene in Escherichia coli BL21(DE3) cells with plasmid pETNicX, for knockout mutants transformation of pKnicX plasmid into Pseudomonas putida KT2440 as recipient, using Escherichia coli DH10B(pKnicX) as donor strain, Escherichia coli HB101 (pRK600) as helper strain