This old version of Proteopedia is provided for student assignments while the new version is undergoing repairs. Content and edits done in this old version of Proteopedia after March 1, 2026 will eventually be lost when it is retired in about June of 2026.
Apply for new accounts at the new Proteopedia. Your logins will work in both the old and new versions.
1poa
From Proteopedia
|
INTERFACIAL CATALYSIS: THE MECHANISM OF PHOSPHOLIPASE A2
Overview
A chemical description of the action of phospholipase A2 (PLA2) can now be, inferred with confidence from three high-resolution x-ray crystal, structures. The first is the structure of the PLA2 from the venom of the, Chinese cobra (Naja naja atra) in a complex with a phosphonate, transition-state analogue. This enzyme is typical of a large, well-studied, homologous family of PLA2S. The second is a similar complex with the, evolutionarily distant bee-venom PLA2. The third structure is the, uninhibited PLA2 from Chinese cobra venom. Despite the different molecular, architectures of the cobra and bee-venom PLA2s, the transition-state, analogue interacts in a nearly identical way with the catalytic machinery, of both enzymes. The disposition of the fatty-acid side chains suggests a, common access route of the substrate from its position in the lipid, aggregate to its productive interaction with the active site. Comparison, of the cobra-venom complex with the uninhibited enzyme indicates that, optimal binding and catalysis at the lipid-water interface is due to, facilitated substrate diffusion from the interfacial binding surface to, the catalytic site rather than an allosteric change in the enzyme's, structure. However, a second bound calcium ion changes its position upon, the binding of the transition-state analogue, suggesting a mechanism for, augmenting the critical electrophile.
About this Structure
1POA is a Single protein structure of sequence from Naja atra with CA as ligand. Active as Phospholipase A(2), with EC number 3.1.1.4 Full crystallographic information is available from OCA.
Reference
Interfacial catalysis: the mechanism of phospholipase A2., Scott DL, White SP, Otwinowski Z, Yuan W, Gelb MH, Sigler PB, Science. 1990 Dec 14;250(4987):1541-6. PMID:2274785
Page seeded by OCA on Tue Nov 20 23:58:07 2007
