1GKM

HISTIDINE AMMONIA-LYASE (HAL) FROM PSEUDOMONAS PUTIDA INHIBITED WITH L-CYSTEINE

Summary for 1GKM

• Entry DOI: 10.2210/pdb1gkm/pdb
• Related: 1B8F 1EB4 1GK2 1GK3 1GKJ
• Descriptor: Histidine ammonia-lyase, CYSTEINE, SULFATE ION, ... (5 entities in total)
• Functional Keywords: lyase, histidine degradation
• Biological source: Pseudomonas putida
• Total number of polymer chains: 1
• Total formula weight: 53944.54

Authors

Baedeker, M.,Schulz, G.E. (deposition date: 2001-08-16, release date: 2002-04-05, Last modification date: 2025-10-01)

Primary citation

Baedeker, M.,Schulz, G.E.
Structures of Two Histidine Ammonia-Lyase Modifications and Implications for the Catalytic Mechanism
Eur.J.Biochem., 269:1790-, 2002

PubMed Abstract: 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.

PubMed: 11895450
DOI: 10.1046/J.1432-1327.2002.02827.X

Experimental method

X-RAY DIFFRACTION (1 Å)