Structure, mechanism, and substrate specificity of kynureninase.
Structure, mechanism, and substrate specificity of kynureninase.
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DOI：
10.1016/j.bbapap.2010.12.003
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发表时间：
2011-11
期刊：
影响因子：
--
通讯作者：
Phillips RS
中科院分区：
文献类型：
--
作者：
Phillips RS
The kynurenine pathway is the major route for tryptophan catabolism in animals and some fungi and bacteria. The procaryotic enzyme preferentially reacts with L-kynurenine, while eucaryotic kynureninases exhibit higher activity with 3-hydroxy-L-kynurenine. Crystallography of kynureninases from Pseudomonas fluorescens (PfKyn) and Homo sapiens (HsKyn) shows that the active sites are nearly identical, except that His-102, Asn-333, and Ser-332 in HsKyn are replaced by Trp-64, Thr-282 and Gly-281 in PfKyn. Site-directed mutagenesis of HsKyn shows that these residues are, at least in part, responsible for the differences in substrate specificity, since the H102W/S332G/N333T triple mutant shows activity with kynurenine but not 3-hydroxykynurenine. PfKyn is strongly inhibited by analogues of a proposed gem-diolate intermediate, dihydrokynurenine and S-(2-aminophenyl)-L-cysteine S,S-dioxide, with Ki values in the low nM range. Stopped-flow kinetic experiments show that a transient quinonoid intermediate is formed on mixing, which decays to a ketimine at 740 s−1. Quench experiments show that anthranilate, the first product, is formed in a stoichiometric burst at 50 s−1, and thus the rate-determining step in the steady state is the release of the second product, L-Ala. β-Benzoylalanine is also a good substrate for PfKyn, but does not show a burst of benzoate formation, indicating that the rate-determining step for this substrate is benzoate release. A Hammett plot of rate constants for substituted β-benzoylalanines is non-linear, suggesting that carbonyl hydration is rate-determining for electron-donating groups, but Cβ-Cγ cleavage is rate-determining for electron-withdrawing groups.
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影响因子：
9.3
作者：
Ting KK;Brew BJ;Guillemin GJ
通讯作者：
Guillemin GJ
DOI：
10.1111/j.1432-1033.1993.tb17953.x
发表时间：
1993-06-01
期刊：
EUROPEAN JOURNAL OF BIOCHEMISTRY
影响因子：
--
作者：
MEHTA, PK;HALE, TI;CHRISTEN, P
通讯作者：
CHRISTEN, P
影响因子：
3.3
作者：
HEYES, MP;BREW, BJ;MARKEY, SP
通讯作者：
MARKEY, SP
影响因子：
3.9
作者：
Koushik, SV;Sundararaju, B;Phillips, RS
通讯作者：
Phillips, RS
影响因子：
15
作者：
Colabroy, KL;Begley, TP
通讯作者：
Begley, TP