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B6db references: 97110315

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
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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