|
type |
Journal Article |
authors |
von Stosch, A. G. |
title |
Aspartate aminotransferase complexed with erythro-beta- hydroxyaspartate: crystallographic and spectroscopic identification of the carbinolamine intermediate |
journal |
Biochemistry |
Activity |
2.6.1.1 |
ui |
97110315 |
year |
(1996) |
volume |
35 |
number |
48 |
pages |
15260-8. |
| |
keywords |
Animal |
abstract |
The crystal structure of mitochondrial aspartate aminotransferase (mAAT) of chicken complexed with erythro-beta-hydroxyaspartate has been determined at 2.4 A resolution. Pregrown crystals of mAAT complexed with the inhibitor maleate (closed enzyme conformation, orthorhombic space group C222(1)) were soaked in solutions of erythro-beta- hydroxyaspartate. The ligand exchange was monitored by microspectrophotometry. The active site turned out to be predominantly occupied by the carbinolamine intermediate. The carbinolamine is a true intermediate of the catalytic cycle forming the last covalently bound enzyme:substrate complex before release of the keto acid product. Occupancies of approximately 80% for the carbinolamine and of approximately 20% for the quinonoid intermediate were obtained. Two hydrogen bonds were identified that are potentially relevant for the accumulation of the carbinolamine intermediate: one to the hydroxyl group of Tyr 70* and the other to the epsilon-NH2 group of Lys 258. |
last changed |
2002/11/04 17:41 |
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