The main purpose of this computational research is to improve the understanding of biocatalysis and receptor triggering by studying the quantum nature of nuclear motion in proteins. Specifically, the research will be focused on three particular biological systems: Soybean lipoxygenase (SLO–1), Monoamine oxidase B (MAO B) and histamine H2 receptor (hisH2). The proposed studies will be devoted to the simulation of proton dynamics and proton transfer in systems containing short H–bonds, which are among the crucial factors for the functionality of enzymes, aimed at uncovering the relationship between the structure and the role of mentioned proteins. The work on SLO–1 should help understand and predict temperature dependence of its exceptionally large H/D kinetic isotope effect of about 80, and to clarify effects of point mutations on its activity. The research on MAO B should elucidate mechanisms of its reactive step and inhibition in the catecholamine dopamine metabolism in the central nervous system, related to the pharmacotherapy of Parkinson disease, depression and age–related cognitive disorders. By using receptor deuteration, the work on hisH2 should unlock the secrets of receptor's distinction between agonists and antagonists binding, which is of major relevance for pharmaceutical industry and drug design. Overall, it is intended to generally identify ubiquitous trends and features that are applicable well beyond the scopes of these individual investigations. During the project the researcher will acquire state–of–the–art methods of computational biochemistry. This represents a major career development as he will be able to later carry on with this leading–edge research in many directions, propelling his scientific independence and maturity. This will lay ground for future project funded within EU initiatives, which will pose the researcher for breakthroughs in the field of enzymology with the promising outlook of pharmaceutical and industrial applications.