1ai3
From Proteopedia
ORBITAL STEERING IN THE CATALYTIC POWER OF ENZYMES: SMALL STRUCTURAL CHANGES WITH LARGE CATALYTIC CONSEQUENCES
Overview
Small structural perturbations in the enzyme isocitrate dehydrogenase (IDH) were made in order to evaluate the contribution of precise substrate alignment to the catalytic power of an enzyme. The reaction trajectory of IDH was modified (i) after the adenine moiety of nicotinamide adenine dinucleotide phosphate was changed to hypoxanthine (the 6-amino was changed to 6-hydroxyl), and (ii) by replacing Mg2+, which has six coordinating ligands, with Ca2+, which has eight coordinating ligands. Both changes make large (10(-3) to 10(-5)) changes in the reaction velocity but only small changes in the orientation of the substrates (both distance and angle) as revealed by cryocrystallographic trapping of active IDH complexes. The results provide evidence that orbital overlap produced by optimal orientation of reacting orbitals plays a major quantitative role in the catalytic power of enzymes.
About this Structure
1AI3 is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.
Reference
Orbital steering in the catalytic power of enzymes: small structural changes with large catalytic consequences., Mesecar AD, Stoddard BL, Koshland DE Jr, Science. 1997 Jul 11;277(5323):202-6. PMID:9211842 Page seeded by OCA on Fri May 2 10:17:56 2008
