The relation between structure and functions is a central topic in enzymology. I propose to study that question at the single molecule level employing a novel optical and force spectroscopy. The enzyme will be linked to a glass surface employing PEG-Biotin-Streptavidin interaction. The location of a single enzyme will be determined by a dye attached to it. The substrate of the reaction, while being non-fluorescent, will be chosen so that its enzymatic reaction product is fluorescent. The time span between fluorescence bursts reflecting the distribution of enzymatic active states will indicate the turnover rate of the enzyme. Contrary to the expectation that an enzyme is characterised by a well defined catalytic rate, a stretched exponential function has been reported to be necessary to fit the the probability distribution of the time span between bursts. I will study the effect of temperature on this stretched exponential behaviour for different enzymes. I will explore the enzymes labelled at two specific position by dyes which can act as donor and acceptor for resonance energy transfer (FRET) and the distance dependent FRET efficiency will offer an insight into the conformation fluctuation of the enzyme. In parallel to the optical observation, I will apply a mechanical tension on the enzymes thereby altering the distribution of its active states. In collaboration with the group of Dr. Marc Baaden, starting from the known enzymatic structure we will study numerically how the tension affects the enzymatic conformations. I will study how this tension alters its functions, via the changes in the distribution of turnover times. These studies will offer an insight into the relation between the structural changes of an enzyme and its measured catalytic activity.