Enzymatic H-Transfer Requires Vibration-Driven Extreme Tunneling

• DOI: 10.1021/bi982719d
• Publication Date: 2002-07-26T05:32:19Z
• Authors: Jaswir Basran; Michael J. Sutcliffe; Nigel S. Scrutton
• Keywords: Oxidoreductases Acting on CH-NH Group Donors; 0303 health sciences; Quinones; Temperature; Tryptophan; Hydrogen Bonding; Methanococcaceae; Substrate Specificity; Kinetics; 03 medical and health sciences; Spectrophotometry; Thermodynamics; Indolequinones; Oxidation-Reduction

Enzymatic breakage of the substrate C−H bond by Methylophilus methyltrophus (sp. W3A1) methylamine dehydrogenase (MADH) has been studied stopped-flow spectroscopy. The rate reduction tryptophan tryptophylquinone (TTQ) cofactor a large kinetic isotope effect (KIE = 16.8 ± 0.5), and KIE is independent temperature. Analysis temperature dependence revealed that extreme (ground state) quantum tunneling responsible for transfer hydrogen nucleus. Reaction rates are strongly dependent on temperature, indicating thermally induced, vibrational motion drives H-transfer reaction. data provide direct experimental evidence enzymatic driven protein scaffold. results demonstrate classical transition state theory its derivatives do not adequately describe this