In:
Protein Science, Wiley, Vol. 17, No. 12 ( 2008-12), p. 2080-2090
Abstract:
In recent years, dihydrodipicolinate synthase (DHDPS, E.C. 4.2.1.52) has received considerable attention from a mechanistic and structural viewpoint. DHDPS catalyzes the reaction of ( S )‐aspartate‐β‐semialdehyde with pyruvate, which is bound via a Schiff base to a conserved active‐site lysine (Lys161 in the enzyme from Escherichia coli ). To probe the mechanism of DHDPS, we have studied the inhibition of E. coli DHDPS by the substrate analog, β‐hydroxypyruvate. The K i was determined to be 0.21 (±0.02) mM, similar to that of the allosteric inhibitor, ( S )‐lysine, and β‐hydroxypyruvate was observed to cause time‐dependent inhibition. The inhibitory reaction with β‐hydroxypyruvate could be qualitatively followed by mass spectrometry, which showed initial noncovalent adduct formation, followed by the slow formation of the covalent adduct. It is unclear whether β‐hydroxypyruvate plays a role in regulating the biosynthesis of meso ‐diaminopimelate and ( S )‐lysine in E. coli , although we note that it is present in vivo . The crystal structure of DHDPS complexed with β‐hydroxypyruvate was solved. The active site clearly showed the presence of the inhibitor covalently bound to the Lys161. Interestingly, the hydroxyl group of β‐hydroxypyruvate was hydrogen‐bonded to the main‐chain carbonyl of Ile203. This provides insight into the possible catalytic role played by this peptide unit, which has a highly strained torsion angle (ω ∼201°). A survey of the known DHDPS structures from other organisms shows this distortion to be a highly conserved feature of the DHDPS active site, and we propose that this peptide unit plays a critical role in catalysis.
Type of Medium:
Online Resource
ISSN:
0961-8368
,
1469-896X
DOI:
10.1110/ps.037440.108
Language:
English
Publisher:
Wiley
Publication Date:
2008
detail.hit.zdb_id:
2000025-X
SSG:
12
Permalink