IR exciton activation mechanism of ethanol oxidation by human alcohol dehydrogenase (ADH) 1A enzyme

Abstract

Low-energy (2500 cm−1) exciton transfer was explored in Müller cell (MC) intermediate filaments (IFs) isolated from porcine retina and filling a capillary matrix. Excitons were generated by absorption of IR radiation at 4 μm. The effects of these excitons on ethanol oxidation by human alcohol dehydrogenase (ADH1A) enzyme were quantified. It was found that IR excitons transferred to the enzyme accelerated alcohol oxidation rate, which increased by the factor of 2.76 when exciting the IFs with 2.39 μW/cm2 of 4 μm IR light. Power dependence of the oxidation rate was also explored. These results show that IFs may be transmitting energy to enzyme molecules in vivo, facilitating enzymatic reactions. The required excitons may be produced by cells at the cost of adenosine triphosphate (ATP) hydrolysis energy. Therefore, such control mechanism for enzymatic reactions may be operational in living systems. Direct activation of the enzyme by IR radiation with 4 μm wavelength did not occur; instead, indirect activation of the IF…ADH1A…NAD (nicotinamide adenine dinucleotide)…EtOH complex occurred by energy transfer of the IR exciton to the ADH1A molecule of this complex. Considering that every living cell has a network of IFs, a similar reaction control mechanism may be operational in vivo, providing a much faster energy supply redirection within the cell than ATP diffusion, and justifying a closer inquiry.