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| [[Image:1gkm.gif|left|200px]] | | {{Seed}} |
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| {{STRUCTURE_1gkm| PDB=1gkm | SCENE= }} | | {{STRUCTURE_1gkm| PDB=1gkm | SCENE= }} |
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| '''HISTIDINE AMMONIA-LYASE (HAL) FROM PSEUDOMONAS PUTIDA INHIBITED WITH L-CYSTEINE'''
| | ===HISTIDINE AMMONIA-LYASE (HAL) FROM PSEUDOMONAS PUTIDA INHIBITED WITH L-CYSTEINE=== |
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| ==Overview==
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| Histidine ammonia-lyase (EC 4.3.1.3) catalyzes the nonoxidative elimination of the alpha-amino group of histidine using a 4-methylidene-imidazole-5-one (MIO), which is formed autocatalytically from the internal peptide segment 142Ala-Ser-Gly. The structure of the enzyme inhibited by a reaction with l-cysteine was established at the very high resolution of 1.0 A. Five active center mutants were produced and their catalytic activities were measured. Among them, mutant Tyr280-->Phe could be crystallized and its structure could be determined at 1.7 A resolution. It contains a planar sp2-hybridized 144-N atom of MIO, in contrast to the pyramidal sp3-hybridized 144-N of the wild-type. With the planar 144-N atom, MIO assumes the conformation of a putative intermediate aromatic state of the reaction, demonstrating that the conformational barrier between aromatic and wild-type states is very low. The data led to a new proposal for the geometry for the catalyzed reaction, which also applies to the closely related phenylalanine ammonia-lyase (EC 4.3.1.5). Moreover, it suggested an intermediate binding site for the released ammonia.
| | The line below this paragraph, {{ABSTRACT_PUBMED_11895450}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 11895450 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_11895450}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Histidine degradation]] | | [[Category: Histidine degradation]] |
| [[Category: Lyase]] | | [[Category: Lyase]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 17:41:51 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 05:26:42 2008'' |